diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index 42b6171c1a83a2..651bc5392b1333 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -823,6 +823,12 @@ mimetypes
   (Contributed by John Franey in :gh:`140937`.)
 * Add ``application/toml``. (Contributed by Gil Forcada in :gh:`139959`.)
 * Add ``image/jxl``. (Contributed by Foolbar in :gh:`144213`.)
+* Add the following MIME types:
+   - ``application/vnd.ms-cab-compressed`` for ``.cab`` extension
+   - ``application/vnd.ms-htmlhelp`` for ``.chm`` extension
+   - ``application/vnd.ms-officetheme`` for ``.thmx`` extension
+(Contributed by Charlie Lin in :gh:`145718`.)
+
 * Rename ``application/x-texinfo`` to ``application/texinfo``.
   (Contributed by Charlie Lin in :gh:`140165`.)
 * Changed the MIME type for ``.ai`` files to ``application/pdf``.
diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index fc916c470a0110..101c6042f0073f 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -509,9 +509,12 @@ def _default_mime_types():
         '.m3u8'   : 'application/vnd.apple.mpegurl',
         '.dll'    : 'application/vnd.microsoft.portable-executable',
         '.exe'    : 'application/vnd.microsoft.portable-executable',
+        '.cab'    : 'application/vnd.ms-cab-compressed',
         '.xls'    : 'application/vnd.ms-excel',
         '.xlb'    : 'application/vnd.ms-excel',
         '.eot'    : 'application/vnd.ms-fontobject',
+        '.chm'    : 'application/vnd.ms-htmlhelp',
+        '.thmx'   : 'application/vnd.ms-officetheme',
         '.ppt'    : 'application/vnd.ms-powerpoint',
         '.pot'    : 'application/vnd.ms-powerpoint',
         '.ppa'    : 'application/vnd.ms-powerpoint',
diff --git a/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst b/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst
new file mode 100644
index 00000000000000..55ef5206c992cd
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-10-01-48-12.gh-issue-145717.dPc0Rt.rst
@@ -0,0 +1 @@
+Add a few Microsoft-specific MIME types.