diff --git a/src/Facades/Endpoint/URL.php b/src/Facades/Endpoint/URL.php
index 86f9affeefe..4eb7182c91c 100644
--- a/src/Facades/Endpoint/URL.php
+++ b/src/Facades/Endpoint/URL.php
@@ -174,6 +174,9 @@ public function removeSiteUrl(?string $url): string
      */
     public function makeRelative(?string $url): string
     {
+        // Normalize duplicate leading slashes before parsing to avoid protocol-relative URL interpretation.
+        $url = preg_replace('#^/+#', '/', (string) $url);
+
         $parsed = parse_url($url);
 
         $url = $parsed['path'] ?? '/';
diff --git a/tests/Facades/UrlTest.php b/tests/Facades/UrlTest.php
index 21dcee85b5d..8986f593271 100644
--- a/tests/Facades/UrlTest.php
+++ b/tests/Facades/UrlTest.php
@@ -642,6 +642,8 @@ public static function relativeProvider()
             'already relative nested route without trailing slash' => ['/foo/page', '/foo/page'],
             'already relative nested route with trailing slash' => ['/foo/page/', '/foo/page'],
             'already relative nested route without leading slash' => ['foo/page', '/foo/page'],
+            'duplicate leading slashes' => ['//page', '/page'],
+            'multiple duplicate leading slashes' => ['////page', '/page'],
 
             'homepage without trailing slash and query param' => ['http://example.com?bar=baz', '/?bar=baz'],
             'homepage with trailing slash and query param' => ['http://example.com/?bar=baz', '/?bar=baz'],