diff --git a/aider/args.py b/aider/args.py
index 588f1dac1..b67aeb43a 100644
--- a/aider/args.py
+++ b/aider/args.py
@@ -491,6 +491,12 @@ def get_parser(default_config_files, git_root):
         default="en",
         help="Specify the language for voice using ISO 639-1 code (default: auto)",
     )
+    group.add_argument(
+        "--chat-language",
+        metavar="CHAT_LANGUAGE",
+        default=None,
+        help="Specify the language to use in the chat (default: None, uses system settings)",
+    )
     group.add_argument(
         "--version",
         action="version",