diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index 6f5d84a3b8ca80..5add5520e10615 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -867,8 +867,17 @@ mimetypes
   - ``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`.)
+  - ``.3gp``   for ``video/3gpp``
+  - ``.3g2``   for ``video/3gpp2``
+  - ``.m4s``   for ``video/iso.segment``
+  - ``.lot``   for ``video/lottie+json``
+  - ``.mj2``   for ``video/mj2``
+  - ``.pyv``   for ``video/vnd.ms-playready.media.pyv``
+  - ``.blk`` and ``.bk2`` for ``video/vnd.radgamettools.bink``
+  - ``.sswf`` and ``.ssw`` for ``video/vnd.sealed.swf``
+  - ``.yt``    for ``video/vnd.youtube.yt``
+
+  (Contributed by Charlie Lin in :gh:`145718` and :gh:`146342`.)
 
 * Add ``image/jxl``. (Contributed by Foolbar in :gh:`144213`.)
 * Rename ``application/x-texinfo`` to ``application/texinfo``.
diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index a834826114614d..bad26188727364 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -668,8 +668,13 @@ def _default_mime_types():
         '.sgml'   : 'text/x-sgml',
         '.vcf'    : 'text/x-vcard',
         '.xml'    : 'text/xml',
+        '.3gp'    : 'video/3gpp',
+        '.3g2'    : 'video/3gpp2',
+        '.m4s'    : 'video/iso.segment',
+        '.lot'    : 'video/lottie+json',
         '.mkv'    : 'video/matroska',
         '.mk3d'   : 'video/matroska-3d',
+        '.mj2'    : 'video/mj2',
         '.mp4'    : 'video/mp4',
         '.mpeg'   : 'video/mpeg',
         '.m1v'    : 'video/mpeg',
@@ -679,6 +684,12 @@ def _default_mime_types():
         '.ogv'    : 'video/ogg',
         '.mov'    : 'video/quicktime',
         '.qt'     : 'video/quicktime',
+        '.pyv'    : 'video/vnd.ms-playready.media.pyv',
+        '.blk'    : 'video/vnd.radgamettools.bink',
+        '.bk2'    : 'video/vnd.radgamettools.bink',
+        '.sswf'   : 'video/vnd.sealed.swf',
+        '.ssw'    : 'video/vnd.sealed.swf',
+        '.yt'     : 'video/vnd.youtube.yt',
         '.webm'   : 'video/webm',
         '.avi'    : 'video/vnd.avi',
         '.m4v'    : 'video/x-m4v',
diff --git a/Misc/NEWS.d/next/Library/2026-03-23-20-14-57.gh-issue-146341.JSTJlL.rst b/Misc/NEWS.d/next/Library/2026-03-23-20-14-57.gh-issue-146341.JSTJlL.rst
new file mode 100644
index 00000000000000..aa0c45ce51826e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-23-20-14-57.gh-issue-146341.JSTJlL.rst
@@ -0,0 +1,13 @@
+Add the following MIME types corresponding to file extensions:
+
+  - ``.3gp``   for ``video/3gpp``
+  - ``.3g2``   for ``video/3gpp2``
+  - ``.m4s``   for ``video/iso.segment``
+  - ``.lot``   for ``video/lottie+json``
+  - ``.mj2``   for ``video/mj2``
+  - ``.pyv``   for ``video/vnd.ms-playready.media.pyv``
+  - ``.blk`` and ``.bk2`` for ``video/vnd.radgamettools.bink``
+  - ``.sswf`` and ``.ssw`` for ``video/vnd.sealed.swf``
+  - ``.yt``    for ``video/vnd.youtube.yt``
+
+(Contributed by Charlie Lin in :gh:`146342`.)