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..73fb1f404 100644
--- a/src/Php84/bootstrap.php
+++ b/src/Php84/bootstrap.php
@@ -15,6 +15,14 @@
     return;
 }
 
+if (defined('CURL_VERSION_HTTP3') || PHP_VERSION_ID < 80200 && function_exists('curl_version') && curl_version()['version'] >= 0x074200) { // libcurl >= 7.66.0
+    define('CURL_HTTP_VERSION_3', 30);
+
+    if (defined('CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256')) { // libcurl >= 7.80.0 (7.88 would be better but is slow to check)
+        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..a1988330a 100644
--- a/tests/Php84/Php84Test.php
+++ b/tests/Php84/Php84Test.php
@@ -64,6 +64,18 @@ public function testArrayAll(array $array, callable $callback, bool $expected)
         $this->assertSame($expected, array_all($array, $callback));
     }
 
+    /**
+     * @requires extension curl
+     */
+    public function testCurlHttp3Constants()
+    {
+        $ch = curl_init();
+        $hasH3 = defined('CURL_VERSION_HTTP3') && (curl_version()['features'] & CURL_VERSION_HTTP3);
+
+        $this->assertSame($hasH3, curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_3));
+        $this->assertSame($hasH3 && defined('CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256'), curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_3ONLY));
+    }
+
     public static function ucFirstDataProvider(): array
     {
         return [