diff --git a/system/HTTP/IncomingRequest.php b/system/HTTP/IncomingRequest.php
index 008a865bcdcd..8012df3eb8e3 100755
--- a/system/HTTP/IncomingRequest.php
+++ b/system/HTTP/IncomingRequest.php
@@ -548,6 +548,18 @@ public function setLocale(string $locale)
         return $this;
     }
 
+    /**
+     * Set the valid locales.
+     *
+     * @return $this
+     */
+    public function setValidLocales(array $locales)
+    {
+        $this->validLocales = $locales;
+
+        return $this;
+    }
+
     /**
      * Gets the current locale, with a fallback to the default
      * locale if none is set.
diff --git a/tests/system/HTTP/IncomingRequestTest.php b/tests/system/HTTP/IncomingRequestTest.php
index f6994f722ce9..2b61850ec579 100644
--- a/tests/system/HTTP/IncomingRequestTest.php
+++ b/tests/system/HTTP/IncomingRequestTest.php
@@ -205,6 +205,21 @@ public function testSetBadLocale()
         $this->assertSame('es', $request->getLocale());
     }
 
+    public function testSetValidLocales()
+    {
+        $config                   = new App();
+        $config->supportedLocales = ['en', 'es'];
+        $config->defaultLocale    = 'es';
+        $config->baseURL          = 'http://example.com/';
+
+        $request = new IncomingRequest($config, new URI(), null, new UserAgent());
+
+        $request->setValidLocales(['ja']);
+        $request->setLocale('ja');
+
+        $this->assertSame('ja', $request->getLocale());
+    }
+
     /**
      * @see https://github.com/codeigniter4/CodeIgniter4/issues/2774
      */
diff --git a/user_guide_src/source/changelogs/v4.4.0.rst b/user_guide_src/source/changelogs/v4.4.0.rst
index 5f902d226f85..1781eaaff0d8 100644
--- a/user_guide_src/source/changelogs/v4.4.0.rst
+++ b/user_guide_src/source/changelogs/v4.4.0.rst
@@ -85,6 +85,7 @@ Others
   ``product/15`` where ``15`` is an arbitrary number.
   See :ref:`controller-default-method-fallback` for details.
 - **Filters:** Now you can use Filter Arguments with :ref:`$filters property <filters-filters-filter-arguments>`.
+- **Request:** Added ``IncomingRequest::setValidLocales()`` method to set valid locales.
 
 Message Changes
 ***************
diff --git a/user_guide_src/source/outgoing/localization.rst b/user_guide_src/source/outgoing/localization.rst
index 2cff7700b091..86769f009f80 100644
--- a/user_guide_src/source/outgoing/localization.rst
+++ b/user_guide_src/source/outgoing/localization.rst
@@ -54,6 +54,9 @@ will be used to set the locale.
 
 Should you ever need to set the locale directly you may use ``IncomingRequest::setLocale(string $locale)``.
 
+Since v4.4.0, ``IncomingRequest::setValidLocales()`` has been added to set
+(and reset) valid locales that are set from ``Config\App::$supportedLocales`` setting.
+
 Content Negotiation
 -------------------