diff --git a/README.md b/README.md
index 91dd2b5c1..7517fba8c 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,7 @@ Polyfills are provided for:
 - the `array_find`, `array_find_key`, `array_any` and `array_all` functions introduced in PHP 8.4;
 - the `Deprecated` attribute introduced in PHP 8.4;
 - the `mb_trim`, `mb_ltrim` and `mb_rtrim` functions introduced in PHP 8.4;
+- the `CURL_HTTP_VERSION_3` and `CURL_HTTP_VERSION_3ONLY` constants introduced in PHP 8.4;
 
 It is strongly recommended to upgrade your PHP version and/or install the missing
 extensions whenever possible. This polyfill should be used only when there is no
diff --git a/src/Php84/README.md b/src/Php84/README.md
index 96921439d..bd56cdc95 100644
--- a/src/Php84/README.md
+++ b/src/Php84/README.md
@@ -6,6 +6,7 @@ This component provides features added to PHP 8.4 core:
 - [`mb_ucfirst` and `mb_lcfirst`](https://wiki.php.net/rfc/mb_ucfirst)
 - [`array_find`, `array_find_key`, `array_any` and `array_all`](https://wiki.php.net/rfc/array_find)
 - [`Deprecated`](https://wiki.php.net/rfc/deprecated_attribute)
+- `CURL_HTTP_VERSION_3` and `CURL_HTTP_VERSION_3ONLY` constants
 
 More information can be found in the
 [main Polyfill README](https://github.com/symfony/polyfill/blob/main/README.md).
diff --git a/src/Php84/bootstrap.php b/src/Php84/bootstrap.php
index 5a86f206f..357c27239 100644
--- a/src/Php84/bootstrap.php
+++ b/src/Php84/bootstrap.php
@@ -15,6 +15,11 @@
     return;
 }
 
+if (!defined('CURL_HTTP_VERSION_3')) {
+    define('CURL_HTTP_VERSION_3', 30);
+    define('CURL_HTTP_VERSION_3ONLY', 31);
+}
+
 if (!function_exists('array_find')) {
     function array_find(array $array, callable $callback) { return p\Php84::array_find($array, $callback); }
 }
diff --git a/tests/Php84/Php84Test.php b/tests/Php84/Php84Test.php
index 1b05902d1..ff36e78c5 100644
--- a/tests/Php84/Php84Test.php
+++ b/tests/Php84/Php84Test.php
@@ -64,6 +64,22 @@ public function testArrayAll(array $array, callable $callback, bool $expected)
         $this->assertSame($expected, array_all($array, $callback));
     }
 
+    public function testCurlHttp3Constants() {
+        if (!function_exists('curl_version')) {
+            $this->markTestSkipped('Curl extension is not available.');
+        }
+
+        // If the curl_version()['features'] bitmask contains the bits for CURL_VERSION_HTTP3,
+        // it means Curl supports HTTP3.
+        if (!(curl_version()['features'] & 33554432)) { // 33554432 = CURL_VERSION_HTTP3
+            $this->markTestSkipped('Curl extension is not built with HTTP3 support');
+        }
+
+        $ch = curl_init();
+        $this->assertTrue(curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_3ONLY));
+        $this->assertTrue(curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_3));
+    }
+
     public static function ucFirstDataProvider(): array
     {
         return [