diff --git a/NEWS b/NEWS
index c59c9a967c40e..a833bf4355ede 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,10 @@ PHP                                                                        NEWS
 - COM:
   . Fix property access of PHP objects wrapped in variant. (cmb)
 
+- Core:
+  . Fixed bug GH-16665 (\array and \callable should not be usable in
+    class_alias). (nielsdos)
+
 - Curl:
   . Added curl_multi_get_handles(). (timwolla)
 
diff --git a/UPGRADING b/UPGRADING
index a336173ffd8b0..13e834f2610a3 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -25,6 +25,10 @@ PHP 8.5 UPGRADE NOTES
   . bzcompress() now throws a ValueError when $work_factor is not between
     0 and 250.
 
+- Core:
+  . It is no longer possible to use "array" and "callable" as class alias names
+    in class_alias().
+
 - LDAP:
   . ldap_get_option() and ldap_set_option() now throw a ValueError when
     passing an invalid option.
diff --git a/Zend/tests/gh16665_1.phpt b/Zend/tests/gh16665_1.phpt
new file mode 100644
index 0000000000000..5baa46a039121
--- /dev/null
+++ b/Zend/tests/gh16665_1.phpt
@@ -0,0 +1,8 @@
+--TEST--
+GH-16665 (\array should not be usable)
+--FILE--
+<?php
+class_alias('stdClass', 'array');
+?>
+--EXPECTF--
+Fatal error: Cannot use "array" as a class alias as it is reserved in %s on line %d
diff --git a/Zend/tests/gh16665_2.phpt b/Zend/tests/gh16665_2.phpt
new file mode 100644
index 0000000000000..3b8ffd4c1e6b0
--- /dev/null
+++ b/Zend/tests/gh16665_2.phpt
@@ -0,0 +1,8 @@
+--TEST--
+GH-16665 (\callable should not be usable)
+--FILE--
+<?php
+class_alias('stdClass', 'callable');
+?>
+--EXPECTF--
+Fatal error: Cannot use "callable" as a class alias as it is reserved in %s on line %d
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index 73bc661cd40e3..ce8fa88dee3c0 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -214,6 +214,10 @@ static const struct reserved_class_name reserved_class_names[] = {
 	{ZEND_STRL("iterable")},
 	{ZEND_STRL("object")},
 	{ZEND_STRL("mixed")},
+	/* These are not usable as class names because they're proper tokens,
+	 * but they are here for class aliases. */
+	{ZEND_STRL("array")},
+	{ZEND_STRL("callable")},
 	{NULL, 0}
 };