- MARCENT (United States Marine Forces Central Command)
- MARCORMATCOM (Marine Corps Materiel Command)
- MARCORSYSCOM (Marine Corps System Command)
- MARDI (Mobile Advanced Robotics Defence Initiative (UK))
- MARDIS (Modernization Army Research and Development System)
- MARDIV (Marine Division (US))
- MARE (Major Accident Response Exercise)
- MARFOR (Marine Corps Forces)
- MARFORCC (Marine Force Component Commander)
- MARFOREUR (Marine Corps Forces, Europe)
- MARFORLANT (Marine Corps Forces, Atlantic)
- MARFORNORTH (Marine Corps Forces, North)
- MARFORPAC (Marine Corps Forces, Pacific)
- MARFORSOUTH (Marine Corps Forces, South)
- MARFORSTRAT (United States Marine Corps Forces, United States Strategic Command)
- MARG (Marine Amphibious Readiness Group)
- MARILYN (Manning and Recruiting in the Lean Years of the Nineties)
- MARINCEN (Maritime Intelligence Center)
- MARINE (Muscles Are Required, Intelligence Not Essential)
- MARINES (My Ass Rides In Navy Equipment and Ships)
- MARK (ED Marketing Educational Consortium)
- MARKS (Multi Access Realtime Knowledge System)
- MARLE (Marine Liaison Element)
- MARLO (Marine Liaison Officer)
- MAROP (Marine Operators)
- MARP (Michigan Association of Railroad Passengers)
- MARPOL (International Convention For The Prevention of Pollution From Ships)
- MARRA (Scratch, Dent, Deface.)
- MARRES (Manuel Radar Reconnaissance Exploitation System)
- MARRS (Martyn Young, Alex Ayuli, Rudy Tambala, Russell Smith, and Steve Young (British electronic music act))
- MARS (Military Amateur Radio Station)