XDM, xdm, or similar can refer to:
Computing X display manager, a part of the X Window System architecture XDM (display manager), the default display manager included with the X Window System XQuery and XPath Data Model Cross-document messaging, that works around the limits set by the same origin policy in a web browser
Firearms Springfield Armory XD-M, a pistol series sold in the United States by Springfield Armory, Inc.
Gaming XDM: X-Treme Dungeon Mastery, a role-playing game supplement by Tracy Hickman, Curtis Hickman and Howard Tayler.
See also "XDM", a song by Overkill from the album White Devil Armory, 2014