diff --git a/post.php b/post.php
index b2ffb7c5..df5e6a72 100644
--- a/post.php
+++ b/post.php
@@ -92,6 +92,43 @@ function check_recaptcha($secret, $response, $remote_ip)
     return !!$resp['success'];
 }
 
+function check_turnstile($secret, $response, $remote_ip, $expected_action)
+{
+    $data = [
+        'secret' => $secret,
+        'response' => $response,
+    ];
+
+    if ($remote_ip !== null) {
+        $data['remoteip'] = $remote_ip;
+    }
+
+    $c = curl_init();
+    curl_setopt_array($c, [
+        CURLOPT_URL => 'https://challenges.cloudflare.com/turnstile/v0/siteverify',
+        CURLOPT_CUSTOMREQUEST => "POST",
+        CURLOPT_POSTFIELDS => $data,
+        CURLOPT_RETURNTRANSFER => true,
+    ]);
+    $c_ret = curl_exec($c);
+    if ($c_ret === false) {
+        $err_no = curl_errno($c);
+        $err_str = curl_error($c);
+
+        curl_close($c);
+        error_log("Turnstide call failed. Curl returned: $err_no ($err_str)");
+        return false;
+    }
+    curl_close($c);
+
+    $json_ret = json_decode($c_ret, true);
+    if ($json_ret === null) {
+        error_log("Turnstide call failed. Malformed json: $c_ret");
+        return false;
+    }
+    return $json_ret['success'] === true && $json_ret['action'] === $expected_action;
+}
+
 /**
  * Deletes the (single) captcha associated with the ip and code.
  *
@@ -690,22 +727,42 @@ function handle_post()
 
 
     if (!$dropped_post) {
-        if ($config['dynamic_captcha'] && $_SERVER['REMOTE_ADDR'] === '127.0.0.1' && $config['recaptcha']) {
-            if (!isset($_POST['g-recaptcha-response'])) {
-                error($config['error']['bot']);
-            }
-            if (!check_recaptcha($config['recaptcha_private'], $_POST['g-recaptcha-response'], null)) {
-                error($config['error']['captcha']);
+        if ($config['dynamic_captcha'] && $_SERVER['REMOTE_ADDR'] === '127.0.0.1') {
+            if ($config['recaptcha']) {
+                if (!isset($_POST['g-recaptcha-response'])) {
+                    error($config['error']['bot']);
+                }
+                if (!check_recaptcha($config['recaptcha_private'], $_POST['g-recaptcha-response'], null)) {
+                    error($config['error']['captcha']);
+                }
+            } elseif ($config['turnstile']) {
+                if (!isset($_POST['cf-turnstile-response'])) {
+                    error($config['error']['bot']);
+                }
+                $expected_action = $post['op'] ? 'post-thread' : 'post-reply';
+                if (!check_turnstile($config['turnstile_private'], $_POST['cf-turnstile-response'], null, $expected_action)) {
+                    error($config['error']['captcha']);
+                }
             }
         }
 
         // Check for CAPTCHA right after opening the board so the "return" link is in there.
-        if (!$config['dynamic_captcha'] && $config['recaptcha']) {
-            if (!isset($_POST['g-recaptcha-response'])) {
-                error($config['error']['bot']);
-            }
-            if (!check_recaptcha($config['recaptcha_private'], $_POST['g-recaptcha-response'], $_SERVER['REMOTE_ADDR'])) {
-                error($config['error']['captcha']);
+        if (!$config['dynamic_captcha']) {
+            if ($config['recaptcha']) {
+                if (!isset($_POST['g-recaptcha-response'])) {
+                    error($config['error']['bot']);
+                }
+                if (!check_recaptcha($config['recaptcha_private'], $_POST['g-recaptcha-response'], $_SERVER['REMOTE_ADDR'])) {
+                    error($config['error']['captcha']);
+                }
+            } elseif ($config['turnstile']) {
+                if (!isset($_POST['cf-turnstile-response'])) {
+                    error($config['error']['bot']);
+                }
+                $expected_action = $post['op'] ? 'post-thread' : 'post-reply';
+                if (!check_turnstile($config['turnstile_private'], $_POST['cf-turnstile-response'], null, $expected_action)) {
+                    error($config['error']['captcha']);
+                }
             }
         }