Mod or MOD may refer to any of the following:

• Mod (or, to use its full name, Modernism) is a lifestyle based around fashion and music that developed in London in the late 1950s. They show an affinity for scooters, such as the Italian Vespas.
  
• Mod is the guitarist of the band Elefant (band).
  

• In mathematics, mod is an abbreviation of the Latin ablative form modulo, introduced by Carl Friedrich Gauss.
• A mod is a festival of Gaelic language arts and culture in Scotland. The Mod (full name, Royal National Mod) is an annual mod, first held in 1892. It has been compared to the Welsh National Eisteddfod.
• Mods (short for modifications) are changes and additions created with editing tools for computer games, particularly for first-person shooters. Common examples would be WAD files for Doom, or the popular multiplayer expansion Counter-Strike for Half-Life.
• MOD is a computer file format for certain music files created with tracker software.
• Internet slang for moderator, a person on an Internet discussion forum who can edit or otherwise change the state of other users' comments, similar to (though less powerful than) sysops.
• Case mods; modifications made to a computer in order to improve its appearance.
• A Modchip, a device used to play import games or circumvent the digital rights management of many popular video game consoles
• mod perl is an optional module for the Apache web server.
• .mod.uk is part of the .uk Domain Name System.
• Mod n cryptanalysis an attack applicable to block and stream ciphers in cryptography

MOD is an abbreviation for

• Magneto-optical disc
• Masters of Deception, was a New York-based hacker group in the late 1980s and early 1990s.
• The Ministry of Defence in the United Kingdom.
• Modular arithmetic
• Multiple organ dysfunction