diff --git a/src/config.cpp b/src/config.cpp
index 47475a04b4d..9f5f0a6ede7 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -504,6 +504,8 @@ namespace config {
       {}  // wa
     },  // display_device
 
+    0,  // manual_rotation
+
     0,  // max_bitrate
     0  // minimum_fps_target (0 = framerate)
   };
@@ -1163,6 +1165,18 @@ namespace config {
       video.dd.wa.hdr_toggle_delay = std::chrono::milliseconds {value};
     }
 
+    {
+      int rotation = 0;
+      int_f(vars, "manual_rotation", rotation);
+      // Normalize to valid rotation values
+      if (rotation == 90 || rotation == 180 || rotation == 270) {
+        video.manual_rotation = rotation;
+      }
+      else {
+        video.manual_rotation = 0;
+      }
+    }
+
     int_f(vars, "max_bitrate", video.max_bitrate);
     double_between_f(vars, "minimum_fps_target", video.minimum_fps_target, {0.0, 1000.0});
 
diff --git a/src/config.h b/src/config.h
index f683647f571..de9e9b8eae6 100644
--- a/src/config.h
+++ b/src/config.h
@@ -140,6 +140,8 @@ namespace config {
       workarounds_t wa;
     } dd;
 
+    int manual_rotation;  ///< Manual display rotation in degrees (0, 90, 180, 270). Useful for portrait panels used in landscape orientation.
+
     int max_bitrate;  // Maximum bitrate, sets ceiling in kbps for bitrate requested from client
     double minimum_fps_target;  ///< Lowest framerate that will be used when streaming. Range 0-1000, 0 = half of client's requested framerate.
   };
diff --git a/src/platform/linux/graphics.cpp b/src/platform/linux/graphics.cpp
index 38eb00717f6..b0d6b692393 100644
--- a/src/platform/linux/graphics.cpp
+++ b/src/platform/linux/graphics.cpp
@@ -7,6 +7,7 @@
 
 // local includes
 #include "graphics.h"
+#include "src/config.h"
 #include "src/file_handler.h"
 #include "src/logging.h"
 #include "src/video.h"
@@ -739,10 +740,19 @@ namespace egl {
 
     sws.serial = std::numeric_limits<std::uint64_t>::max();
 
+    // When rotation is 90 or 270 degrees, swap input dimensions for aspect ratio calculation
+    // because the shader will rotate the texture, effectively swapping width and height
+    int effective_in_width = in_width;
+    int effective_in_height = in_height;
+    if (config::video.manual_rotation == 90 || config::video.manual_rotation == 270) {
+      effective_in_width = in_height;
+      effective_in_height = in_width;
+    }
+
     // Ensure aspect ratio is maintained
-    auto scalar = std::fminf(out_width / (float) in_width, out_height / (float) in_height);
-    auto out_width_f = in_width * scalar;
-    auto out_height_f = in_height * scalar;
+    auto scalar = std::fminf(out_width / (float) effective_in_width, out_height / (float) effective_in_height);
+    auto out_width_f = effective_in_width * scalar;
+    auto out_height_f = effective_in_height * scalar;
 
     // result is always positive
     auto offsetX_f = (out_width - out_width_f) / 2;
@@ -831,6 +841,15 @@ namespace egl {
     gl::ctx.UseProgram(sws.program[1].handle());
     gl::ctx.Uniform1fv(loc_width_i, 1, &width_i);
 
+    // Set rotation uniform on UV shader (program[1])
+    {
+      int rotation = config::video.manual_rotation;
+      auto loc_rotation = gl::ctx.GetUniformLocation(sws.program[1].handle(), "rotation");
+      if (loc_rotation >= 0) {
+        gl::ctx.Uniform1i(loc_rotation, rotation);
+      }
+    }
+
     auto color_p = video::color_vectors_from_colorspace({video::colorspace_e::rec601, false, 8}, true);
     std::pair<const char *, std::string_view> members[] {
       std::make_pair("color_vec_y", util::view(color_p->color_vec_y)),
@@ -855,6 +874,23 @@ namespace egl {
     sws.program[0].bind(sws.color_matrix);
     sws.program[1].bind(sws.color_matrix);
 
+    // Set rotation uniform on Y shader (program[0]) and Scene/Cursor shader (program[2])
+    {
+      int rotation = config::video.manual_rotation;
+
+      gl::ctx.UseProgram(sws.program[0].handle());
+      auto loc_rot_y = gl::ctx.GetUniformLocation(sws.program[0].handle(), "rotation");
+      if (loc_rot_y >= 0) {
+        gl::ctx.Uniform1i(loc_rot_y, rotation);
+      }
+
+      gl::ctx.UseProgram(sws.program[2].handle());
+      auto loc_rot_scene = gl::ctx.GetUniformLocation(sws.program[2].handle(), "rotation");
+      if (loc_rot_scene >= 0) {
+        gl::ctx.Uniform1i(loc_rot_scene, rotation);
+      }
+    }
+
     gl::ctx.BlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
     gl_drain_errors;
diff --git a/src_assets/common/assets/web/configs/tabs/AudioVideo.vue b/src_assets/common/assets/web/configs/tabs/AudioVideo.vue
index cc6a88110b3..975339f856b 100644
--- a/src_assets/common/assets/web/configs/tabs/AudioVideo.vue
+++ b/src_assets/common/assets/web/configs/tabs/AudioVideo.vue
@@ -85,6 +85,18 @@ const config = ref(props.config)
       :config="config"
     />
 
+    <!-- Manual Rotation (Linux only) -->
+    <div class="mb-3" v-if="platform === 'linux'">
+      <label for="manual_rotation" class="form-label">{{ $t('config.manual_rotation') }}</label>
+      <select id="manual_rotation" class="form-select" v-model="config.manual_rotation">
+        <option value="0">{{ $t('config.manual_rotation_0') }}</option>
+        <option value="90">{{ $t('config.manual_rotation_90') }}</option>
+        <option value="180">{{ $t('config.manual_rotation_180') }}</option>
+        <option value="270">{{ $t('config.manual_rotation_270') }}</option>
+      </select>
+      <div class="form-text">{{ $t('config.manual_rotation_desc') }}</div>
+    </div>
+
     <DisplayDeviceOptions
       :platform="platform"
       :config="config"
diff --git a/src_assets/common/assets/web/public/assets/locale/en.json b/src_assets/common/assets/web/public/assets/locale/en.json
index 75b1a9c74d5..7c7453d78df 100644
--- a/src_assets/common/assets/web/public/assets/locale/en.json
+++ b/src_assets/common/assets/web/public/assets/locale/en.json
@@ -261,6 +261,12 @@
     "locale_desc": "The locale used for Sunshine's user interface.",
     "log_path": "Logfile Path",
     "log_path_desc": "The file where the current logs of Sunshine are stored.",
+    "manual_rotation": "Manual Display Rotation",
+    "manual_rotation_0": "0° (No rotation)",
+    "manual_rotation_90": "90° (Clockwise)",
+    "manual_rotation_180": "180° (Upside down)",
+    "manual_rotation_270": "270° (Counter-clockwise)",
+    "manual_rotation_desc": "Manually rotate the captured display output. Useful for portrait panels used in landscape orientation (e.g. Steam Deck) where KMS reports the raw panel resolution instead of the logical orientation.",
     "max_bitrate": "Maximum Bitrate",
     "max_bitrate_desc": "The maximum bitrate (in Kbps) that Sunshine will encode the stream at. If set to 0, it will always use the bitrate requested by Moonlight.",
     "minimum_fps_target": "Minimum FPS Target",
diff --git a/src_assets/linux/assets/shaders/opengl/ConvertUV.vert b/src_assets/linux/assets/shaders/opengl/ConvertUV.vert
index 70c14f4c231..2665913e044 100644
--- a/src_assets/linux/assets/shaders/opengl/ConvertUV.vert
+++ b/src_assets/linux/assets/shaders/opengl/ConvertUV.vert
@@ -5,8 +5,22 @@ precision mediump float;
 #endif
 
 uniform float width_i;
+uniform int rotation;
 
 out vec3 uuv;
+
+// Note: duplicated in Scene.vert (no shader include mechanism available)
+vec2 rotate_uv(vec2 uv, int rot) {
+	if (rot == 90) {
+		return vec2(uv.y, 1.0 - uv.x);
+	} else if (rot == 180) {
+		return vec2(1.0 - uv.x, 1.0 - uv.y);
+	} else if (rot == 270) {
+		return vec2(1.0 - uv.y, uv.x);
+	}
+	return uv;
+}
+
 //--------------------------------------------------------------------------------------
 // Vertex Shader
 //--------------------------------------------------------------------------------------
@@ -18,10 +32,13 @@ void main()
 	float x = idHigh * 4.0 - 1.0;
 	float y = idLow * 4.0 - 1.0;
 
-	float u_right = idHigh * 2.0;
-	float u_left = u_right - width_i;
-	float v = idLow * 2.0;
+	float u_base = idHigh * 2.0;
+	float v_base = idLow * 2.0;
+
+	// Apply rotation to texture coordinates
+	vec2 uv_right = rotate_uv(vec2(u_base, v_base), rotation);
+	vec2 uv_left = rotate_uv(vec2(u_base - width_i, v_base), rotation);
 
-	uuv = vec3(u_left, u_right, v);
+	uuv = vec3(uv_left.x, uv_right.x, uv_right.y);
 	gl_Position = vec4(x, y, 0.0, 1.0);
-}
\ No newline at end of file
+}
diff --git a/src_assets/linux/assets/shaders/opengl/Scene.vert b/src_assets/linux/assets/shaders/opengl/Scene.vert
index 24c16bef1d5..50bf4969043 100644
--- a/src_assets/linux/assets/shaders/opengl/Scene.vert
+++ b/src_assets/linux/assets/shaders/opengl/Scene.vert
@@ -4,8 +4,22 @@
 precision mediump float;
 #endif
 
+uniform int rotation;
+
 out vec2 tex;
 
+// Note: duplicated in ConvertUV.vert (no shader include mechanism available)
+vec2 rotate_uv(vec2 uv, int rot) {
+	if (rot == 90) {
+		return vec2(uv.y, 1.0 - uv.x);
+	} else if (rot == 180) {
+		return vec2(1.0 - uv.x, 1.0 - uv.y);
+	} else if (rot == 270) {
+		return vec2(1.0 - uv.y, uv.x);
+	}
+	return uv;
+}
+
 void main()
 {
 	float idHigh = float(gl_VertexID >> 1);
@@ -18,5 +32,5 @@ void main()
 	float v = idLow * 2.0;
 
 	gl_Position = vec4(x, y, 0.0, 1.0);
-	tex = vec2(u, v);
-}
\ No newline at end of file
+	tex = rotate_uv(vec2(u, v), rotation);
+}
diff --git a/tests/unit/test_config.cpp b/tests/unit/test_config.cpp
new file mode 100644
index 00000000000..46b525895c5
--- /dev/null
+++ b/tests/unit/test_config.cpp
@@ -0,0 +1,73 @@
+/**
+ * @file tests/unit/test_config.cpp
+ * @brief Test src/config.cpp
+ */
+#include "../tests_common.h"
+
+// standard includes
+#include <string>
+#include <unordered_map>
+
+// local includes
+#include <src/config.h>
+
+// Forward-declare the internal apply_config function for testing
+namespace config {
+  void apply_config(std::unordered_map<std::string, std::string> &&vars);
+}
+
+class ManualRotationTest: public ::testing::TestWithParam<std::pair<std::string, int>> {
+protected:
+  void SetUp() override {
+    // Reset to default before each test
+    config::video.manual_rotation = 0;
+  }
+};
+
+TEST_P(ManualRotationTest, ParsesRotationValues) {
+  auto [input, expected] = GetParam();
+
+  std::unordered_map<std::string, std::string> vars;
+  vars["manual_rotation"] = input;
+  config::apply_config(std::move(vars));
+
+  EXPECT_EQ(config::video.manual_rotation, expected);
+}
+
+INSTANTIATE_TEST_SUITE_P(
+  ConfigTests,
+  ManualRotationTest,
+  testing::Values(
+    // Valid rotation values
+    std::make_pair("0", 0),
+    std::make_pair("90", 90),
+    std::make_pair("180", 180),
+    std::make_pair("270", 270),
+    // Invalid values should normalize to 0
+    std::make_pair("45", 0),
+    std::make_pair("360", 0),
+    std::make_pair("-90", 0),
+    std::make_pair("1", 0),
+    std::make_pair("abc", 0)
+  ),
+  [](const testing::TestParamInfo<ManualRotationTest::ParamType> &info) {
+    auto input = info.param.first;
+    // Replace non-alphanumeric chars for valid test name
+    std::replace_if(
+      input.begin(), input.end(),
+      [](char c) { return !std::isalnum(c); },
+      '_'
+    );
+    return "rotation_" + input;
+  }
+);
+
+TEST(ManualRotationDefaultTest, DefaultIsZero) {
+  // Reset config and apply empty vars to verify default
+  config::video.manual_rotation = 999;
+  std::unordered_map<std::string, std::string> vars;
+  vars["manual_rotation"] = "0";
+  config::apply_config(std::move(vars));
+
+  EXPECT_EQ(config::video.manual_rotation, 0);
+}