diff --git a/system/HTTP/SiteURIFactory.php b/system/HTTP/SiteURIFactory.php
index c87898c0470e..e920ba1634b3 100644
--- a/system/HTTP/SiteURIFactory.php
+++ b/system/HTTP/SiteURIFactory.php
@@ -111,8 +111,40 @@ public function detectRoutePath(string $protocol = ''): string
      */
     private function parseRequestURI(): string
     {
+        $appConfig = $this->appConfig;
+        $baseUrl   = $appConfig->baseURL;
+        $indexPage = $appConfig->indexPage;
+        $baseUri   = false;
+        $parsedUrl = parse_url($baseUrl);
+
+        if (isset($parsedUrl['path'])) { // The path could be empty if the url is just a domain
+            $baseUri = $parsedUrl['path'];
+        }
+        if ($baseUri) {
+            $baseUriArray = explode('/', $baseUri);
+            $baseUriArray = array_filter($baseUriArray); // We remove the empty strings from the array
+            $baseUri      = implode('/', $baseUriArray); // We join the array back into a string with slashes
+            if ($baseUri !== '') {
+                $baseUri = '/' . $baseUri; // We add a slash at the beginning of the base Uri as implode will not do that
+            } else {
+                $baseUri = false;
+            }
+        }
+
+        $serverRequestUri = $this->superglobals->server('REQUEST_URI'); // We get the request URI from the server superglobals
+
+        if (null !== $serverRequestUri) {
+            if ($baseUri && str_starts_with($serverRequestUri, $baseUri)) {
+                $serverRequestUri = substr($serverRequestUri, strlen($baseUri));
+            } // We remove the base Uri from the request URI if it exists, baseUri is the path to the subdirectory
+            if ($indexPage !== false && str_starts_with($serverRequestUri, '/' . $indexPage)) {
+                $serverRequestUri = substr($serverRequestUri, strlen('/' . $indexPage));
+            } // We remove the index page from the request URI if it exists
+            $serverRequestUri = '/' . ltrim($serverRequestUri, '/'); // makes sure that the uri starts with a slash
+        }
+
         if (
-            $this->superglobals->server('REQUEST_URI') === null
+            $serverRequestUri === null
             || $this->superglobals->server('SCRIPT_NAME') === null
         ) {
             return '';
@@ -122,7 +154,7 @@ private function parseRequestURI(): string
         // string contains a colon followed by a number. So we attach a dummy
         // host since REQUEST_URI does not include the host. This allows us to
         // parse out the query string and path.
-        $parts = parse_url('http://dummy' . $this->superglobals->server('REQUEST_URI'));
+        $parts = parse_url('http://dummy' . $serverRequestUri);
         $query = $parts['query'] ?? '';
         $path  = $parts['path'] ?? '';
 
diff --git a/tests/system/HTTP/SiteURIFactoryTest.php b/tests/system/HTTP/SiteURIFactoryTest.php
index b26fde04b245..737e2d8ddeb1 100644
--- a/tests/system/HTTP/SiteURIFactoryTest.php
+++ b/tests/system/HTTP/SiteURIFactoryTest.php
@@ -171,4 +171,53 @@ public static function provideCreateFromStringWithoutIndexPage(): iterable
             ],
         ];
     }
+
+    #[DataProvider('provideCreateFromStringWithIndexPageSubDirCombinations')]
+    public function testCreateFromStringWithIndexPageSubDirCombinations(
+        string $subDir,
+        string $indexPage,
+    ): void {
+        $standardUrl        = 'http://localhost:8080';
+        $standardScriptName = '/public/index.php';
+
+        $route                = 'controller/method';
+        $appConfig            = new App();
+        $appConfig->baseURL   = $standardUrl . $subDir;
+        $appConfig->indexPage = $indexPage;
+
+        $_SERVER['PATH_INFO']   = '/' . $route;
+        $_SERVER['REQUEST_URI'] = $subDir . '/' . $indexPage . $_SERVER['PATH_INFO'];
+        $_SERVER['SCRIPT_NAME'] = $subDir . $standardScriptName;
+        $_SERVER['HTTP_HOST']   = $standardUrl;
+
+        $factory           = $this->createSiteURIFactory($appConfig);
+        $detectedRoutePath = $factory->detectRoutePath();
+        $this->assertSame($route, $detectedRoutePath);
+    }
+
+    public static function provideCreateFromStringWithIndexPageSubDirCombinations(): iterable
+    {
+        return [
+            'no subdir and no index' => [
+                '',
+                '',
+            ],
+            'no subdir and index' => [
+                '',
+                'index.php',
+            ],
+            'subdir and no index' => [
+                '/subdir',
+                '',
+            ],
+            'subdir and index' => [
+                '/subdir',
+                'index.php',
+            ],
+            'subdir 2 levels deep string and index' => [
+                '/subdir/subsubdir',
+                'index.php',
+            ],
+        ];
+    }
 }