diff --git a/Cargo.lock b/Cargo.lock
index 1a14cbf5..b11e1b2d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -588,6 +588,12 @@ version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
 
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
 [[package]]
 name = "encoding"
 version = "0.2.33"
@@ -1271,6 +1277,7 @@ version = "0.0.0"
 dependencies = [
  "bytes",
  "cookie",
+ "either",
  "encoding",
  "futures",
  "h2",
@@ -1768,6 +1775,7 @@ version = "0.28.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf85e27e86080aafd5a22eae58a162e133a589551542b3e5cee4beb27e54f8e1"
 dependencies = [
+ "either",
  "libc",
  "once_cell",
  "portable-atomic",
diff --git a/impit-node/src/lib.rs b/impit-node/src/lib.rs
index 8657d537..456ae6fc 100644
--- a/impit-node/src/lib.rs
+++ b/impit-node/src/lib.rs
@@ -120,7 +120,7 @@ impl ImpitWrapper {
       timeout: request_init
         .as_ref()
         .and_then(|init| init.timeout)
-        .map(|timeout| Duration::from_millis(timeout.into())),
+        .map(|timeout| Some(Duration::from_millis(timeout.into()))),
       http3_prior_knowledge: request_init
         .as_ref()
         .and_then(|init| init.force_http3)
diff --git a/impit-python/Cargo.toml b/impit-python/Cargo.toml
index e49fb0da..f0d3e36a 100644
--- a/impit-python/Cargo.toml
+++ b/impit-python/Cargo.toml
@@ -15,9 +15,10 @@ h2 = "0.4.7"
 reqwest = "0.13.1"
 tokio-stream = "0.1.17"
 bytes = "1.9.0"
-pyo3 = { version = "0.28", features = ["extension-module", "auto-initialize"] }
+pyo3 = { version = "0.28", features = ["extension-module", "auto-initialize", "either"] }
 pyo3-async-runtimes = { version = "0.28", features = ["attributes", "async-std-runtime", "tokio-runtime"] }
 urlencoding = "2.1.3"
 encoding = "0.2.33"
 cookie = "0.18.1"
 futures = "0.3.31"
+either = "1.15.0"
diff --git a/impit-python/python/impit/__init__.py b/impit-python/python/impit/__init__.py
index d809788e..de7b311c 100644
--- a/impit-python/python/impit/__init__.py
+++ b/impit-python/python/impit/__init__.py
@@ -3,6 +3,7 @@
 
 from .cookies import Cookies
 from .impit import (
+    USE_CLIENT_DEFAULT,
     AsyncClient,
     Client,
     CloseError,
@@ -48,6 +49,7 @@
 __version__ = metadata.version('impit')
 
 __all__ = [
+    'USE_CLIENT_DEFAULT',
     'AsyncClient',
     'Browser',
     'Client',
diff --git a/impit-python/python/impit/impit.pyi b/impit-python/python/impit/impit.pyi
index f769b347..f66df365 100644
--- a/impit-python/python/impit/impit.pyi
+++ b/impit-python/python/impit/impit.pyi
@@ -9,6 +9,13 @@ from contextlib import AbstractAsyncContextManager, AbstractContextManager
 
 Browser = Literal['chrome', 'firefox', 'chrome125', 'chrome100', 'chrome101', 'chrome104', 'chrome107', 'chrome110', 'chrome116', 'chrome131', 'chrome136', 'chrome142', 'firefox128', 'firefox133', 'firefox135', 'firefox144']
 
+USE_CLIENT_DEFAULT: str
+"""Sentinel that, when passed as a per-request ``timeout``, causes the client-level default timeout to be used.
+
+This is the default value for the ``timeout`` parameter in per-request methods.
+Pass ``None`` instead to disable the timeout entirely.
+"""
+
 class HTTPError(Exception):
     """Represents an HTTP-related error."""
 
@@ -397,7 +404,7 @@ class Client:
                 .. warning::
                     Not supported when HTTP/3 is enabled.
             timeout:
-                Default request timeout in seconds.
+                Default request timeout in seconds. Pass ``None`` to disable the timeout entirely.
 
                 This value can be overridden for individual requests.
             verify:
@@ -459,7 +466,7 @@ class Client:
         browser: Browser | None = None,
         http3: bool | None = None,
         proxy: str | None = None,
-        timeout: float | None = None,
+        timeout: float | None = ...,
         verify: bool | None = None,
         default_encoding: str | None = None,
         follow_redirects: bool | None = None,
@@ -475,7 +482,7 @@ class Client:
             browser: Browser to impersonate ("chrome" or "firefox")
             http3: Enable HTTP/3 support
             proxy: Proxy URL to use
-            timeout: Default request timeout in seconds
+            timeout: Default request timeout in seconds. Pass ``None`` to disable the timeout entirely.
             verify: Verify SSL certificates (set to False to ignore TLS errors)
             default_encoding: Default encoding for response.text field (e.g., "utf-8", "cp1252"). Overrides `content-type`
                 header and bytestream prescan.
@@ -495,7 +502,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a GET request.
@@ -505,7 +512,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -515,7 +522,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a POST request.
@@ -525,7 +532,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
 
         """
@@ -536,7 +543,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a PUT request.
@@ -546,7 +553,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -556,7 +563,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a PATCH request.
@@ -566,7 +573,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -576,7 +583,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a DELETE request.
@@ -586,7 +593,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -596,7 +603,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a HEAD request.
@@ -606,7 +613,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -616,7 +623,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an OPTIONS request.
@@ -626,7 +633,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -636,7 +643,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make a TRACE request.
@@ -646,7 +653,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -657,7 +664,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
         stream: bool = False,
     ) -> Response:
@@ -669,7 +676,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
             stream: Whether to return a streaming response (default: False)
         """
@@ -681,7 +688,7 @@ class Client:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> AbstractContextManager[Response]:
         """Make a streaming request with the specified method.
@@ -703,7 +710,7 @@ class Client:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -739,7 +746,7 @@ class AsyncClient:
                 .. warning::
                     Not supported when HTTP/3 is enabled.
             timeout:
-                Default request timeout in seconds.
+                Default request timeout in seconds. Pass ``None`` to disable the timeout entirely.
 
                 This value can be overridden for individual requests.
             verify:
@@ -800,7 +807,7 @@ class AsyncClient:
         browser: Browser | None = None,
         http3: bool | None = None,
         proxy: str | None = None,
-        timeout: float | None = None,
+        timeout: float | None = ...,
         verify: bool | None = None,
         default_encoding: str | None = None,
         follow_redirects: bool | None = None,
@@ -816,7 +823,7 @@ class AsyncClient:
             browser: Browser to impersonate ("chrome" or "firefox")
             http3: Enable HTTP/3 support
             proxy: Proxy URL to use
-            timeout: Default request timeout in seconds
+            timeout: Default request timeout in seconds. Pass ``None`` to disable the timeout entirely.
             verify: Verify SSL certificates (set to False to ignore TLS errors)
             default_encoding: Default encoding for response.text field (e.g., "utf-8", "cp1252"). Overrides `content-type`
                 header and bytestream prescan.
@@ -836,7 +843,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous GET request.
@@ -846,7 +853,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -856,7 +863,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous POST request.
@@ -866,7 +873,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
 
         """
@@ -877,7 +884,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous PUT request.
@@ -887,7 +894,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -897,7 +904,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous PATCH request.
@@ -907,7 +914,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -917,7 +924,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous DELETE request.
@@ -927,7 +934,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -937,7 +944,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous HEAD request.
@@ -947,7 +954,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -957,7 +964,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous OPTIONS request.
@@ -967,7 +974,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -977,7 +984,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> Response:
         """Make an asynchronous TRACE request.
@@ -987,7 +994,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -998,7 +1005,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
         stream: bool = False,
     ) -> Response:
@@ -1010,7 +1017,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
             stream: Whether to return a streaming response (default: False)
         """
@@ -1022,7 +1029,7 @@ class AsyncClient:
         content: bytes | bytearray | list[int] | None = None,
         data: dict[str, str] | None = None,
         headers: dict[str, str] | None = None,
-        timeout: float | None = None,
+        timeout: float | str | None = USE_CLIENT_DEFAULT,
         force_http3: bool | None = None,
     ) -> AbstractAsyncContextManager[Response]:
         """Make an asynchronous streaming request with the specified method.
@@ -1044,7 +1051,7 @@ class AsyncClient:
             content: Raw content to send
             data: Form data to send in request body
             headers: HTTP headers for this request. Override both client-level and impersonation headers (case-insensitive). To remove an impersonated header, pass an empty string as the value
-            timeout: Request timeout in seconds (overrides default timeout)
+            timeout: Per-request timeout in seconds. Pass ``None`` to disable the timeout entirely. Defaults to ``USE_CLIENT_DEFAULT`` (inherits the client-level timeout).
             force_http3: Force HTTP/3 protocol
         """
 
@@ -1055,7 +1062,7 @@ def stream(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1088,7 +1095,7 @@ def get(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1121,7 +1128,7 @@ def post(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1154,7 +1161,7 @@ def put(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1187,7 +1194,7 @@ def patch(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1220,7 +1227,7 @@ def delete(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1253,7 +1260,7 @@ def head(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1286,7 +1293,7 @@ def options(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
@@ -1316,7 +1323,7 @@ def trace(
     content: bytes | bytearray | list[int] | None = None,
     data: dict[str, str] | None = None,
     headers: dict[str, str] | None = None,
-    timeout: float | None = None,
+    timeout: float | str | None = USE_CLIENT_DEFAULT,
     force_http3: bool | None = None,
     follow_redirects: bool | None = None,
     max_redirects: int | None = None,
diff --git a/impit-python/src/async_client.rs b/impit-python/src/async_client.rs
index 422f8cd5..13a55698 100644
--- a/impit-python/src/async_client.rs
+++ b/impit-python/src/async_client.rs
@@ -1,5 +1,6 @@
 use std::{collections::HashMap, sync::Arc, time::Duration};
 
+use either::{Either, Right};
 use impit::{
     errors::ImpitError,
     impit::{Impit, ImpitBuilder},
@@ -8,8 +9,10 @@ use impit::{
 use pyo3::{exceptions::PyTypeError, ffi::c_str, prelude::*};
 
 use crate::{
-    cookies::PythonCookieJar, errors::ImpitPyError, request::form_to_bytes,
-    response::ImpitPyResponse, RequestBody,
+    cookies::PythonCookieJar,
+    errors::ImpitPyError,
+    request::{form_to_bytes, parse_timeout, RequestBody, USE_CLIENT_DEFAULT_SENTINEL},
+    response::ImpitPyResponse,
 };
 
 #[pyclass]
@@ -38,13 +41,13 @@ impl AsyncClient {
     }
 
     #[new]
-    #[pyo3(signature = (browser=None, http3=None, proxy=None, timeout=None, verify=None, default_encoding=None, follow_redirects=None, max_redirects=Some(20), cookie_jar=None, cookies=None, headers=None, local_address=None))]
+    #[pyo3(signature = (browser=None, http3=None, proxy=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), verify=None, default_encoding=None, follow_redirects=None, max_redirects=Some(20), cookie_jar=None, cookies=None, headers=None, local_address=None))]
     pub fn new(
         py: Python<'_>,
         browser: Option<String>,
         http3: Option<bool>,
         proxy: Option<String>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         verify: Option<bool>,
         default_encoding: Option<String>,
         follow_redirects: Option<bool>,
@@ -107,8 +110,9 @@ impl AsyncClient {
             None => builder,
         };
 
-        let builder = match timeout {
-            Some(secs) => builder.with_default_timeout(Duration::from_secs_f64(secs)),
+        let builder = match parse_timeout(timeout)? {
+            Some(Some(d)) => builder.with_default_timeout(d),
+            Some(None) => builder.with_default_timeout(Duration::MAX),
             None => builder,
         };
 
@@ -160,7 +164,7 @@ impl AsyncClient {
         })
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn get<'python>(
         &self,
         py: Python<'python>,
@@ -168,7 +172,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -184,7 +188,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn head<'python>(
         &self,
         py: Python<'python>,
@@ -192,7 +196,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -208,7 +212,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn post<'python>(
         &self,
         py: Python<'python>,
@@ -216,7 +220,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -232,7 +236,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn patch<'python>(
         &self,
         py: Python<'python>,
@@ -240,7 +244,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -256,7 +260,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn put<'python>(
         &self,
         py: Python<'python>,
@@ -264,7 +268,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -280,7 +284,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn delete<'python>(
         &self,
         py: Python<'python>,
@@ -288,7 +292,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -304,7 +308,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn options<'python>(
         &self,
         py: Python<'python>,
@@ -312,7 +316,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -328,7 +332,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn trace<'python>(
         &self,
         py: Python<'python>,
@@ -336,7 +340,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         self.request(
@@ -352,7 +356,7 @@ impl AsyncClient {
         )
     }
 
-    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn stream<'python>(
         &self,
         py: Python<'python>,
@@ -361,7 +365,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
         let response = self.request(
@@ -398,7 +402,7 @@ impl AsyncClient {
         Ok(wrapped_response.into_bound(py))
     }
 
-    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=None, force_http3=false, stream=false))]
+    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false, stream=false))]
     pub fn request<'python>(
         &self,
         py: Python<'python>,
@@ -407,7 +411,7 @@ impl AsyncClient {
         content: Option<Vec<u8>>,
         mut data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
         stream: Option<bool>,
     ) -> Result<pyo3::Bound<'python, PyAny>, PyErr> {
@@ -434,13 +438,15 @@ impl AsyncClient {
             None => Ok(Vec::new()),
         }?;
 
+        let timeout = parse_timeout(timeout)?;
+
         let options = RequestOptions {
             headers: headers
                 .unwrap_or_default()
                 .iter()
                 .map(|(k, v)| (k.clone(), v.clone()))
                 .collect(),
-            timeout: timeout.map(Duration::from_secs_f64),
+            timeout,
             http3_prior_knowledge: force_http3.unwrap_or(false),
         };
 
diff --git a/impit-python/src/client.rs b/impit-python/src/client.rs
index ef90352a..d5192f2d 100644
--- a/impit-python/src/client.rs
+++ b/impit-python/src/client.rs
@@ -1,5 +1,6 @@
 use std::{collections::HashMap, time::Duration};
 
+use either::{Either, Right};
 use impit::{
     errors::ImpitError,
     impit::{Impit, ImpitBuilder},
@@ -10,7 +11,7 @@ use pyo3::{ffi::c_str, prelude::*};
 use crate::{
     cookies::PythonCookieJar,
     errors::ImpitPyError,
-    request::{form_to_bytes, RequestBody},
+    request::{form_to_bytes, parse_timeout, RequestBody, USE_CLIENT_DEFAULT_SENTINEL},
     response::{self, ImpitPyResponse},
 };
 
@@ -35,13 +36,13 @@ impl Client {
     }
 
     #[new]
-    #[pyo3(signature = (browser=None, http3=None, proxy=None, timeout=None, verify=None, default_encoding=None, follow_redirects=None, max_redirects=Some(20), cookie_jar=None, cookies=None, headers=None, local_address=None))]
+    #[pyo3(signature = (browser=None, http3=None, proxy=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), verify=None, default_encoding=None, follow_redirects=None, max_redirects=Some(20), cookie_jar=None, cookies=None, headers=None, local_address=None))]
     pub fn new(
         py: Python<'_>,
         browser: Option<String>,
         http3: Option<bool>,
         proxy: Option<String>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         verify: Option<bool>,
         default_encoding: Option<String>,
         follow_redirects: Option<bool>,
@@ -98,8 +99,11 @@ impl Client {
             None => builder,
         };
 
-        let builder = match timeout {
-            Some(secs) => builder.with_default_timeout(Duration::from_secs_f64(secs)),
+        let builder = match parse_timeout(timeout)
+            .map_err(|e| ImpitPyError(ImpitError::BindingPassthroughError(e.to_string())))?
+        {
+            Some(Some(d)) => builder.with_default_timeout(d),
+            Some(None) => builder.with_default_timeout(Duration::MAX),
             None => builder,
         };
 
@@ -151,7 +155,7 @@ impl Client {
         })
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn get(
         &self,
         py: Python<'_>,
@@ -159,7 +163,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -175,7 +179,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn head(
         &self,
         py: Python<'_>,
@@ -183,7 +187,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -199,7 +203,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn post(
         &self,
         py: Python<'_>,
@@ -207,7 +211,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -223,7 +227,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn patch(
         &self,
         py: Python<'_>,
@@ -231,7 +235,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -247,7 +251,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn put(
         &self,
         py: Python<'_>,
@@ -255,7 +259,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -271,7 +275,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn delete(
         &self,
         py: Python<'_>,
@@ -279,7 +283,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -295,7 +299,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn options(
         &self,
         py: Python<'_>,
@@ -303,7 +307,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -319,7 +323,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn trace(
         &self,
         py: Python<'_>,
@@ -327,7 +331,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<response::ImpitPyResponse, ImpitPyError> {
         self.request(
@@ -343,7 +347,7 @@ impl Client {
         )
     }
 
-    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=None, force_http3=false))]
+    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false))]
     pub fn stream<'python>(
         &self,
         py: Python<'python>,
@@ -352,7 +356,7 @@ impl Client {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
     ) -> Result<Bound<'python, PyAny>, PyErr> {
         let response = self.request(
@@ -389,7 +393,7 @@ impl Client {
         Ok(wrapped_response.into_bound(py))
     }
 
-    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=None, force_http3=false, stream=false))]
+    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false, stream=false))]
     pub fn request(
         &self,
         py: Python<'_>,
@@ -398,7 +402,7 @@ impl Client {
         content: Option<Vec<u8>>,
         mut data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
         stream: Option<bool>,
     ) -> Result<ImpitPyResponse, ImpitPyError> {
@@ -425,13 +429,16 @@ impl Client {
             None => Ok(Vec::new()),
         }?;
 
+        let timeout = parse_timeout(timeout)
+            .map_err(|e| ImpitPyError(ImpitError::BindingPassthroughError(e.to_string())))?;
+
         let options = RequestOptions {
             headers: headers
                 .unwrap_or_default()
                 .iter()
                 .map(|(k, v)| (k.clone(), v.clone()))
                 .collect(),
-            timeout: timeout.map(Duration::from_secs_f64),
+            timeout,
             http3_prior_knowledge: force_http3.unwrap_or(false),
         };
 
diff --git a/impit-python/src/lib.rs b/impit-python/src/lib.rs
index b6d2cf66..21ff3f1b 100644
--- a/impit-python/src/lib.rs
+++ b/impit-python/src/lib.rs
@@ -1,3 +1,4 @@
+use either::{Either, Right};
 use pyo3::prelude::*;
 
 mod async_client;
@@ -9,7 +10,7 @@ mod response;
 
 use async_client::AsyncClient;
 use client::Client;
-use request::RequestBody;
+use request::{RequestBody, USE_CLIENT_DEFAULT_SENTINEL};
 use std::collections::HashMap;
 
 #[pymodule]
@@ -87,14 +88,14 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
     ($($name:ident),*) => {
         $(
             #[pyfunction]
-            #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=None, force_http3=false, cookie_jar=None, cookies=None, follow_redirects=None, max_redirects=None, proxy=None))]
+            #[pyo3(signature = (url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false, cookie_jar=None, cookies=None, follow_redirects=None, max_redirects=None, proxy=None))]
             fn $name(
                 _py: Python,
                 url: String,
                 content: Option<Vec<u8>>,
                 data: Option<RequestBody>,
                 headers: Option<HashMap<String, String>>,
-                timeout: Option<f64>,
+                timeout: Option<Either<f64, &str>>,
                 force_http3: Option<bool>,
                 cookie_jar: Option<pyo3::Bound<'_, pyo3::PyAny>>,
                 cookies: Option<pyo3::Bound<'_, pyo3::PyAny>>,
@@ -102,7 +103,7 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
                 max_redirects: Option<u16>,
                 proxy: Option<String>,
             ) -> Result<response::ImpitPyResponse, errors::ImpitPyError> {
-                let client = Client::new(_py, None, None, proxy, None, None, None, follow_redirects, max_redirects, cookie_jar, cookies, None, None);
+                let client = Client::new(_py, None, None, proxy, Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), None, None, follow_redirects, max_redirects, cookie_jar, cookies, None, None);
 
                 client?.$name(_py, url, content, data, headers, timeout, force_http3)
             }
@@ -115,7 +116,7 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
     http_no_client!(get, post, put, head, patch, delete, options, trace);
 
     #[pyfunction]
-    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=None, force_http3=false, cookie_jar=None, cookies=None, follow_redirects=None, max_redirects=None, proxy=None))]
+    #[pyo3(signature = (method, url, content=None, data=None, headers=None, timeout=Some(Right(USE_CLIENT_DEFAULT_SENTINEL)), force_http3=false, cookie_jar=None, cookies=None, follow_redirects=None, max_redirects=None, proxy=None))]
     fn stream<'python>(
         _py: Python<'python>,
         method: &str,
@@ -123,7 +124,7 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
         content: Option<Vec<u8>>,
         data: Option<RequestBody>,
         headers: Option<HashMap<String, String>>,
-        timeout: Option<f64>,
+        timeout: Option<Either<f64, &str>>,
         force_http3: Option<bool>,
         cookie_jar: Option<pyo3::Bound<'_, pyo3::PyAny>>,
         cookies: Option<pyo3::Bound<'_, pyo3::PyAny>>,
@@ -136,7 +137,7 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
             None,
             None,
             proxy,
-            None,
+            Some(Right(USE_CLIENT_DEFAULT_SENTINEL)),
             None,
             None,
             follow_redirects,
@@ -161,5 +162,7 @@ fn impit(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
 
     m.add_function(wrap_pyfunction!(stream, m)?)?;
 
+    m.add("USE_CLIENT_DEFAULT", USE_CLIENT_DEFAULT_SENTINEL)?;
+
     Ok(())
 }
diff --git a/impit-python/src/request.rs b/impit-python/src/request.rs
index 00e26221..07a26da6 100644
--- a/impit-python/src/request.rs
+++ b/impit-python/src/request.rs
@@ -1,6 +1,39 @@
-use std::collections::HashMap;
+use std::{collections::HashMap, time::Duration};
 
-use pyo3::{Bound, FromPyObject, PyAny};
+use either::{Either, Left, Right};
+use pyo3::{Bound, PyAny};
+
+/// The sentinel string used as the Python default value for per-request `timeout` parameters.
+///
+/// When a user does not explicitly supply a `timeout`, this string is received by the Rust
+/// method and treated as "inherit the client-level default".  It is exposed to Python as
+/// the `USE_CLIENT_DEFAULT` module constant so that callers can also pass it explicitly.
+pub(crate) const USE_CLIENT_DEFAULT_SENTINEL: &str = "USE_CLIENT_DEFAULT";
+/// Parse a Python `timeout` argument into `Option<Option<Duration>>`:
+///
+/// - `USE_CLIENT_DEFAULT_SENTINEL` string (not provided / explicit sentinel) → `None`
+///   (inherit client default)
+/// - Python `None` → `Some(None)` (disable timeout)
+/// - Python `float` → `Some(Some(Duration))` (specific timeout)
+pub(crate) fn parse_timeout(
+    timeout: Option<Either<f64, &str>>,
+) -> pyo3::PyResult<Option<Option<Duration>>> {
+    match timeout {
+        None => Ok(Some(None)),
+        Some(Left(secs)) => Ok(Some(Some(Duration::from_secs_f64(secs)))),
+        Some(Right(s)) => {
+            if s != USE_CLIENT_DEFAULT_SENTINEL {
+                Err(pyo3::exceptions::PyValueError::new_err(format!(
+                    "Invalid timeout value: {s:?}"
+                )))
+            } else {
+                Ok(None)
+            }
+        }
+    }
+}
+
+use pyo3::FromPyObject;
 
 #[derive(FromPyObject)]
 pub(crate) enum RequestBody<'py> {
diff --git a/impit-python/test/basic_client_test.py b/impit-python/test/basic_client_test.py
index 3f61accd..635738d0 100644
--- a/impit-python/test/basic_client_test.py
+++ b/impit-python/test/basic_client_test.py
@@ -7,7 +7,18 @@
 
 import pytest
 
-from impit import Browser, Client, Cookies, StreamClosed, StreamConsumed, TooManyRedirects
+from impit import (
+    USE_CLIENT_DEFAULT,
+    Browser,
+    Client,
+    ConnectTimeout,
+    Cookies,
+    ReadTimeout,
+    StreamClosed,
+    StreamConsumed,
+    TimeoutException,
+    TooManyRedirects,
+)
 
 from .httpbin import get_httpbin_url
 from .setup_proxy import start_proxy_server
@@ -599,3 +610,84 @@ def test_iter_bytes_without_consumed(self, browser: Browser) -> None:
 
         with pytest.raises(StreamClosed):
             _ = response.content
+
+
+def make_slow_server(port_holder: list[int], delay: float = 2.0) -> None:
+    """Start a server in a daemon thread that waits `delay` seconds before responding."""
+    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    server.bind(('127.0.0.1', 0))
+    port_holder[0] = server.getsockname()[1]
+    server.listen(1)
+
+    def _serve() -> None:
+        try:
+            conn, _ = server.accept()
+            conn.recv(1024)
+            time.sleep(delay)
+            conn.send(b'HTTP/1.1 200 OK\r\nContent-Length: 2\r\n\r\nOK')
+            conn.close()
+        finally:
+            server.close()
+
+    threading.Thread(target=_serve, daemon=True).start()
+
+
+class TestTimeoutBehaviour:
+    def test_timeout_none_disables_timeout(self) -> None:
+        """timeout=None should disable the timeout entirely, not use the client default."""
+
+        port_holder = [0]
+        # Start a slow server (responds after 1.5s)
+        make_slow_server(port_holder, delay=1.5)
+        time.sleep(0.05)
+
+        impit = Client(timeout=0.1)
+
+        # Without explicit timeout override the client default (0.1s) should fire.
+        with pytest.raises((TimeoutException, ConnectTimeout, ReadTimeout)):
+            impit.get(f'http://127.0.0.1:{port_holder[0]}/')
+
+        # Restart the slow server for the second request.
+        port_holder2 = [0]
+        make_slow_server(port_holder2, delay=1.5)
+        time.sleep(0.05)
+
+        # With timeout=None the timeout is disabled → request succeeds despite slow server.
+        response = impit.get(f'http://127.0.0.1:{port_holder2[0]}/', timeout=None)
+        assert response.status_code == 200
+
+    def test_use_client_default_uses_client_timeout(self) -> None:
+        """USE_CLIENT_DEFAULT should use the client-level timeout."""
+
+        port_holder = [0]
+        make_slow_server(port_holder, delay=1.5)
+        time.sleep(0.05)
+
+        impit = Client(timeout=0.1)
+
+        # Explicitly passing USE_CLIENT_DEFAULT should behave the same as not passing timeout.
+        with pytest.raises((TimeoutException, ConnectTimeout, ReadTimeout)):
+            impit.get(f'http://127.0.0.1:{port_holder[0]}/', timeout=USE_CLIENT_DEFAULT)
+
+    def test_client_timeout_none_disables_default_timeout(self) -> None:
+        """Client(timeout=None) should disable the timeout for all requests by default."""
+
+        port_holder = [0]
+        make_slow_server(port_holder, delay=1.5)
+        time.sleep(0.05)
+
+        impit = Client(timeout=None)
+        response = impit.get(f'http://127.0.0.1:{port_holder[0]}/')
+        assert response.status_code == 200
+
+    def test_client_timeout_none_overridden_by_per_request(self) -> None:
+        """A per-request timeout should override Client(timeout=None)."""
+
+        port_holder = [0]
+        make_slow_server(port_holder, delay=1.5)
+        time.sleep(0.05)
+
+        impit = Client(timeout=None)
+        with pytest.raises((TimeoutException, ConnectTimeout, ReadTimeout)):
+            impit.get(f'http://127.0.0.1:{port_holder[0]}/', timeout=0.1)
diff --git a/impit/src/impit.rs b/impit/src/impit.rs
index d48f48a2..6e6cb9f8 100644
--- a/impit/src/impit.rs
+++ b/impit/src/impit.rs
@@ -506,7 +506,13 @@ impl<CookieStoreImpl: CookieStore + 'static> Impit<CookieStoreImpl> {
         let headers = request_options.headers;
         let request = self.build_request(method, url, body, headers);
 
-        let timeout = request_options.timeout;
+        let timeout = match request_options.timeout {
+            None => None,
+            // reqwest has no per-request "no timeout" API; overriding with Duration::MAX is the
+            // conventional way to disable a timeout without rebuilding the client.
+            Some(None) => Some(Duration::MAX),
+            Some(Some(d)) => Some(d),
+        };
         let http3_prior_knowledge = request_options.http3_prior_knowledge;
         self.send(request, timeout, Some(http3_prior_knowledge))
             .await
diff --git a/impit/src/request.rs b/impit/src/request.rs
index b15714dc..a0f1d0ad 100644
--- a/impit/src/request.rs
+++ b/impit/src/request.rs
@@ -12,8 +12,12 @@ pub struct RequestOptions {
     /// A `Vec` of string pairs that represent custom HTTP request headers. These take precedence over the headers set in [`ImpitBuilder`](crate::impit::ImpitBuilder)
     /// (both from the `with_headers` and the `with_browser` methods).
     pub headers: Vec<(String, String)>,
-    /// The timeout for the request. This option overrides the global [`Impit`] timeout.
-    pub timeout: Option<Duration>,
+    /// The per-request timeout, with three possible states:
+    ///
+    /// - `None` — inherit the client-level default timeout set via [`ImpitBuilder::with_default_timeout`](crate::impit::ImpitBuilder::with_default_timeout).
+    /// - `Some(None)` — disable the timeout entirely for this request (wait indefinitely).
+    /// - `Some(Some(d))` — use the given duration, overriding the client-level default.
+    pub timeout: Option<Option<Duration>>,
     /// Enforce the use of HTTP/3 for this request. This will cause broken responses from servers that don't support HTTP/3.
     ///
     /// If [`ImpitBuilder::with_http3`](crate::impit::ImpitBuilder::with_http3) wasn't called, this option will cause [`ErrorType::Http3Disabled`](crate::impit::ErrorType::Http3Disabled) errors.