diff --git a/Cabal/src/Distribution/Simple/Setup/Config.hs b/Cabal/src/Distribution/Simple/Setup/Config.hs
index a1bb8b299f0..237b4dd0f6e 100644
--- a/Cabal/src/Distribution/Simple/Setup/Config.hs
+++ b/Cabal/src/Distribution/Simple/Setup/Config.hs
@@ -206,8 +206,6 @@ data ConfigFlags = ConfigFlags
   , configExactConfiguration :: Flag Bool
   -- ^ All direct dependencies and flags are provided on the command line by
   --  the user via the '--dependency' and '--flags' options.
-  , configFlagError :: Flag String
-  -- ^ Halt and show an error message indicating an error in flag assignment
   , configRelocatable :: Flag Bool
   -- ^ Enable relocatable package built
   , configDebugInfo :: Flag DebugInfoLevel
@@ -319,7 +317,6 @@ instance Eq ConfigFlags where
       && equal configCoverage
       && equal configLibCoverage
       && equal configExactConfiguration
-      && equal configFlagError
       && equal configRelocatable
       && equal configDebugInfo
       && equal configDumpBuildInfo
@@ -366,7 +363,6 @@ defaultConfigFlags progDb =
     , configCoverage = Flag False
     , configLibCoverage = NoFlag
     , configExactConfiguration = Flag False
-    , configFlagError = NoFlag
     , configRelocatable = Flag False
     , configDebugInfo = Flag NoDebugInfo
     , configDumpBuildInfo = NoFlag
diff --git a/cabal-install/src/Distribution/Client/Config.hs b/cabal-install/src/Distribution/Client/Config.hs
index 9036932b6b2..08008d6dc06 100644
--- a/cabal-install/src/Distribution/Client/Config.hs
+++ b/cabal-install/src/Distribution/Client/Config.hs
@@ -544,7 +544,6 @@ instance Semigroup SavedConfig where
           , configCoverage = combine configCoverage
           , configLibCoverage = combine configLibCoverage
           , configExactConfiguration = combine configExactConfiguration
-          , configFlagError = combine configFlagError
           , configRelocatable = combine configRelocatable
           , configUseResponseFiles = combine configUseResponseFiles
           , configDumpBuildInfo = combine configDumpBuildInfo
diff --git a/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs b/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
index 37ffb185db1..aa3e4403056 100644
--- a/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
+++ b/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
@@ -1140,7 +1140,6 @@ convertToLegacyAllPackageConfig
           , configLibCoverage = mempty -- TODO: don't merge
           , configExactConfiguration = mempty
           , configBenchmarks = mempty
-          , configFlagError = mempty -- TODO: ???
           , configRelocatable = mempty
           , configDebugInfo = mempty
           , configUseResponseFiles = mempty
@@ -1216,7 +1215,6 @@ convertToLegacyPerPackageConfig PackageConfig{..} =
         , configLibCoverage = packageConfigCoverage -- TODO: don't merge
         , configExactConfiguration = mempty
         , configBenchmarks = packageConfigBenchmarks
-        , configFlagError = mempty -- TODO: ???
         , configRelocatable = packageConfigRelocatable
         , configDebugInfo = packageConfigDebugInfo
         , configUseResponseFiles = mempty
diff --git a/cabal-install/src/Distribution/Client/ProjectPlanning.hs b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
index 685e46dfa77..015e257e467 100644
--- a/cabal-install/src/Distribution/Client/ProjectPlanning.hs
+++ b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
@@ -4166,7 +4166,6 @@ setupHsConfigureFlags
         ElabComponent _ -> mempty
 
       configExactConfiguration = toFlag True
-      configFlagError = mempty -- TODO: [research required] appears not to be implemented
       configScratchDir = mempty -- never use
       configUserInstall = mempty -- don't rely on defaults
       configPrograms_ = mempty -- never use, shouldn't exist
diff --git a/changelog.d/pr-11480.md b/changelog.d/pr-11480.md
new file mode 100644
index 00000000000..5b7aa7d3294
--- /dev/null
+++ b/changelog.d/pr-11480.md
@@ -0,0 +1,8 @@
+---
+synopsis: Remove unused config flag `configFlagError`
+packages: [Cabal, cabal-install]
+prs: 11480
+---
+
+Remove unused config flag `configFlagError`. This was added, but never used in any external
+or internal behavior.