diff --git a/src/php/src/Api/Documentation/Attributes/ApiResponse.php b/src/php/src/Api/Documentation/Attributes/ApiResponse.php
index 222350b..ee35835 100644
--- a/src/php/src/Api/Documentation/Attributes/ApiResponse.php
+++ b/src/php/src/Api/Documentation/Attributes/ApiResponse.php
@@ -64,7 +64,7 @@ readonly class ApiResponse
             302 => 'Found (redirect)',
             304 => 'Not modified',
             400 => 'Bad request',
-            401 => 'Unauthorized',
+            401 => 'Unauthorised',
             403 => 'Forbidden',
             404 => 'Not found',
             405 => 'Method not allowed',
diff --git a/src/php/src/Api/Documentation/Extensions/ApiKeyAuthExtension.php b/src/php/src/Api/Documentation/Extensions/ApiKeyAuthExtension.php
index baf0259..0344700 100644
--- a/src/php/src/Api/Documentation/Extensions/ApiKeyAuthExtension.php
+++ b/src/php/src/Api/Documentation/Extensions/ApiKeyAuthExtension.php
@@ -53,7 +53,7 @@ class ApiKeyAuthExtension implements Extension
             'properties' => [
                 'message' => [
                     'type' => 'string',
-                    'example' => 'This action is unauthorized.',
+                    'example' => 'This action is unauthorised.',
                 ],
             ],
         ];
diff --git a/src/php/src/Api/Middleware/AuthenticateApiKey.php b/src/php/src/Api/Middleware/AuthenticateApiKey.php
index 839ed4e..ecddfc5 100644
--- a/src/php/src/Api/Middleware/AuthenticateApiKey.php
+++ b/src/php/src/Api/Middleware/AuthenticateApiKey.php
@@ -116,7 +116,7 @@ class AuthenticateApiKey
     }
 
     /**
-     * Return 401 Unauthorized response.
+     * Return 401 Unauthorised response.
      */
     protected function unauthorized(string $message): Response
     {
diff --git a/src/php/src/Api/Resources/ErrorResource.php b/src/php/src/Api/Resources/ErrorResource.php
index ca62eca..a39ba38 100644
--- a/src/php/src/Api/Resources/ErrorResource.php
+++ b/src/php/src/Api/Resources/ErrorResource.php
@@ -40,7 +40,7 @@ class ErrorResource extends JsonResource
     /**
      * Common error factory methods.
      */
-    public static function unauthorized(string $message = 'Unauthorized'): static
+    public static function unauthorized(string $message = 'Unauthorised'): static
     {
         return new static('unauthorized', $message);
     }
diff --git a/src/php/src/Api/Tests/Feature/OpenApiDocumentationComprehensiveTest.php b/src/php/src/Api/Tests/Feature/OpenApiDocumentationComprehensiveTest.php
index 8bf742c..f185b05 100644
--- a/src/php/src/Api/Tests/Feature/OpenApiDocumentationComprehensiveTest.php
+++ b/src/php/src/Api/Tests/Feature/OpenApiDocumentationComprehensiveTest.php
@@ -398,7 +398,7 @@ describe('ApiResponse Attribute Rendering', function () {
             201 => 'Resource created',
             204 => 'No content',
             400 => 'Bad request',
-            401 => 'Unauthorized',
+            401 => 'Unauthorised',
             403 => 'Forbidden',
             404 => 'Not found',
             422 => 'Validation error',
@@ -724,7 +724,7 @@ describe('Extension System', function () {
 // ─────────────────────────────────────────────────────────────────────────────
 
 describe('Error Response Documentation', function () {
-    it('documents 401 Unauthorized response', function () {
+    it('documents 401 Unauthorised response', function () {
         $extension = new ApiKeyAuthExtension;
         $spec = [
             'info' => [],