diff --git a/packages/markitdown/src/markitdown/_markitdown.py b/packages/markitdown/src/markitdown/_markitdown.py
index 702b10c6..c7fd5de9 100644
--- a/packages/markitdown/src/markitdown/_markitdown.py
+++ b/packages/markitdown/src/markitdown/_markitdown.py
@@ -107,6 +107,7 @@ def __init__(
         requests_session = kwargs.get("requests_session")
         if requests_session is None:
             self._requests_session = requests.Session()
+            self._requests_session.headers.update({'User-Agent': 'MarkItDown'})
         else:
             self._requests_session = requests_session