diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index caecc11c37cb4c..afc053f135ddfb 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -451,6 +451,7 @@ def _default_mime_types():
         '.mht'    : 'message/rfc822',
         '.mhtml'  : 'message/rfc822',
         '.mif'    : 'application/x-mif',
+        '.mjs'    : 'application/javascript',
         '.mov'    : 'video/quicktime',
         '.movie'  : 'video/x-sgi-movie',
         '.mp2'    : 'audio/mpeg',
diff --git a/Misc/NEWS.d/next/Library/2018-08-15-16-22-30.bpo-31715.Iw8jS8.rst b/Misc/NEWS.d/next/Library/2018-08-15-16-22-30.bpo-31715.Iw8jS8.rst
new file mode 100644
index 00000000000000..eacba28f9fd987
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-08-15-16-22-30.bpo-31715.Iw8jS8.rst
@@ -0,0 +1 @@
+Associate ``.mjs`` file extension with ``application/javascript`` MIME Type.