diff --git a/NEWS b/NEWS
index 5be5ffd18ac4..45f40a076078 100644
--- a/NEWS
+++ b/NEWS
@@ -83,6 +83,7 @@ PHP                                                                        NEWS
     recursive array references). (alexandre-daubois)
   . Fixed bug GH-21223; mb_guess_encoding no longer crashes when passed huge
     list of candidate encodings (with 200,000+ entries). (Jordi Kroon)
+  . mbregex has been deprecated. (youkidearitai)
 
 - Mysqli:
   . Added mysqli_quote_string() and mysqli::quote_string(). (Kamil Tekiela)
diff --git a/UPGRADING b/UPGRADING
index 6c6115ebcc84..df81eb889699 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -154,6 +154,11 @@ PHP 8.6 UPGRADE NOTES
 4. Deprecated Functionality
 ========================================
 
+- Mbstring:
+  . Mbregex has been deprecated, because the underlying Oniguruma library
+    is no longer maintained.
+    RFC: https://wiki.php.net/rfc/eol-oniguruma
+
 ========================================
 5. Changed Functions
 ========================================