| M |
| M | Mach number |
| M | Million |
| M&S | Maintenance & Supply |
| M/T | Measurement Ton |
| MA | Military Assistance |
| MA&IS | Military Assistance and International Security Office, OSD |
| MAAG | Military Assistance Advisory Group. Subsumed under MACV in 1962 and merged in 1964. |
| MAB | Marine Amphibious Base |
| MAB | Marine Amphibious Brigade |
| MAC | Marine Amphibious Corps |
| MAC | Military Affairs Committee |
| MAC | Military Airlift Command |
| MAC | Military Assistance Command |
| MACAG | Military Assistance Command, Adjutant General |
| MACCD | Military Assistance Command Construction Directorate |
| MACCE | Directorate of Communications-Electronics |
| MACCH | Military Assistance Command, Chaplain |
| MACCO | Military Assistance Command, Comptroller |
| MACCOC | Military Assistance Command Combat Operation Center |
| MACCORDS | Military Assistance Command Civil Operations and Revolutionary/Rural Development Support |
| MACDC | Military Assistance Command, Directorate of Construction |
| MACDI | Military Assistance Command, Directorate of Intelligence |
| MACDL | Military Assistance Command, Directorate of Logistics |
| MACDMA | Military Assistance Command, Data Management Agency |
| MACDP | Military Assistance Command, Directorate of Personnel |
| MACEA | Military Assistance Command, Economic Affairs |
| MACEVAL | Operations Research /Systems Analysis, Hqs MACV |
| MACFWMAO | Military Assistance Command Free World Military Assistance Office |
| MACIG | Military Assistance Command Inspector General |
| MACJ# | Military Assistance Staff Section (#) |
| MACJ* | Military Assistance Staff Section (*) |
| MACJ1 | Military Assistance Command, Assistant Chief of Staff for Personnel |
| MACJ2 | Military Assistance Command, Assistant Chief of Staff for Intelligence |
| MACJ3 | Military Assistance Command, Assistant Chief of Staff for Operations |
| MACJ4 | Military Assistance Command, Assistant Chief of Staff for Logistics |
| MACJ5 | Military Assistance Command, Assistant Chief of Staff for Plans |
| MACJ6 | Military Assistance Command, Assistant Chief of Staff for Communications - Electronics |
| MACJA | Military Assistance Command, Judge Advocate |
| MACJOIR | Deputy to COMUSMACV for CORDS |
| MACJOO | COMUSMACV |
| MACMA | Military Assistance Command, Military Assistance |
| MACMD | Military Assistance Command, Surgeon |
| MACOI | Military Assistance Command, Office of Information |
| MACONOMY | MACV Economy Program |
| MACORDS | Asst Chief of Staff for Civil Operations and Revolutionary Development Support, Hqs MACV MACJA |
| MACPD | Military Assistance Command Political Warfare Advisory Directorate |
| MACPD | Military Assistance Command, Psychological Operations Directorate |
| MACPM | Military Assistance Command, Provost Marshall |
| MACSA | Military Assistance Command, Science Advisor |
| MACSOG | Military Assistance Command, Studies and Observation Group |
| MACST | Military Assistance Command, Special Troops |
| MACT | Military Assistance Command, Training Directorate |
| MACTC | Military Assistance Command, Technical Assistance Coordinator |
| MACTHAI | Military Assistance Command, Thailand |
| MACV | Military Assistance Command, Vietnam |
| MACVDAC | Military Assistance Command, Vietnam Distribution and Allocation Committee |
| MACVFWD | Military Assistance Command Vietnam, Forward |
| MACVIG | Military Assistance Command, Vietnam, Inspector General |
| MACVSA | Science Advisor, Hqs MACV |
| MAD | Antisubmarine Magnetic Anomaly Detector |
| MADV | Mobilisation and War Veterans Advisory Branch |
| MAF | Marine Amphibious Force |
| MAG | Marine Air Group |
| MAGROCV | Military Advisory Group, Republic of China, Vietnam |
| MAGV | Military Assistance Group, Vietnam |
| MAI | Military Assistance Institute |
| Maint | Maintenance |
| MAJ | Major |
| Maj Gen | Major General |
| MAL | Material Requirements List |
| MALT | Mobile Advisory Logistics Team |
| MAP | Military Assistance Program |
| MAPC | Military Affairs Party Committee |
| MAPEX | Military Assistance Program Excess Material Program |
| Mar | Marine |
| Mar Div | Marine Division |
| Mar/MAR REGT | Marine Infantry Regiment |
| MARADVU | Marine Advisory Unit |
| MARCORPS | Marine Corps |
| MARDIV | Marine Division |
| MARKET TIME | USN anti-infiltration blockade of SVN Coast. |
| MARS | Military Affiliate Radio Station |
| MASF | Military Assistance Service Funded |
| MASFP | Military Assistance Service Funded Program |
| MASH | Mobile Army Surgical Hospital |
| MAT | Military Advisory Team |
| MAT | Mobile Advisory Team |
| MATA | Military Advisor Training Assistance |
| MATP | Military Assistance Training Program |
| MATS | Military Air Transport Service |
| MATSB | Mobile Advanced Tactical Support Base |
| MATT | Mobile Advisory Training Team |
| MATTLO | Military Attache Liaison Office |
| MATTS | Military Air Terminal Transportation Service |
| MAU | Marine Amphibious Unit |
| MAW | Marine Air Wing |
| MBA | Military Base Agreement |
| MBBL | Thousand Barrels |
| MBBLS | Thousand Barrels |
| MBE | Materials Handling Equipment |
| MBF | Military Banking Facility |
| MC | Medical Corps |
| MCA | Military Construction, Army |
| MCAF | Military Construction. Air Force |
| MCAS | Marine Corps Air Station |
| MCB | Mobile Construction Battalion |
| MCDEC | Marine Corps Development and Education Command |
| MCI | Army Meal Combat Individual |
| MCID | Mufti-purpose Concealed Intrusion Detector |
| MCM | Mine Countermeasures Measures |
| MCN | Military Construction, Navy |
| MCP | Malayan Communist Party |
| MCP | Military Construction Program |
| MCS | Mine Countermeasure Support Ship |
| MDAP | Material Defense Assistance Program |
| MDD | Municipal Development Directorate |
| MDEM | Ministry for the Development of Ethnic Minorities |
| MDMAF | Mekong Delta Mobile Afloat Force |
| MDMRF | Mekong Delta Mobile Riverine Force |
| MEAL | Military Economic-Action Committee |
| MEB | Marine Expeditionary Brigade |
| Mech/MECH | Mechanized |
| MED | Materiel Exploitation Division |
| MED | Medical |
| MEDCAP | Medical Civic Action Program |
| MEDCOMV | Medical Commander, Vietnam |
| Medevac/MEDEVAC | Medical Evacuation |
| MEDT | Military Equipment Delivery Team |
| MEDTC | Military Equipment Delivery Team, Cambodia |
| MEE | Mission Essential Equipment |
| MEF | Marine Expeditionary Force |
| MEIP | Miscellaneous Environmental Improvement Program |
| MEMI | Master Equipment Management Index |
| MEMO | Memorandum |
| MER | Multiple Ejection Rack |
| MEW | Maintenance Engineering Wing |
| MF | Main Force |
| MFGP | Main Force Group |
| MFR | Memorandum for Record |
| MFYP | MOND Four Year Plan |
| MG | Machine gun |
| MG | Major General |
| Mgt | Management |
| MH | Medal of Honor |
| MHB | Military History Branch, Hqs MACV |
| MHE | Materials Handling Equipment |
| MI | Mile |
| MI | Military Intelligence |
| MIA | Missing in Action |
| MIC | Military Intelligence Center |
| MICH | Minister of Information and Chieu Hoi |
| MID | Mine Interdiction Division |
| Mig/MIG | Soviet Aircraft designed by Mikoyan and Gurevich |
| MIG SCREEN | Mission wherein protecting fighters are placed between the threat and the protected force in a specific area. |
| MIGCAP | Combat air patrol mission whose actions are directed against MIG aircraft. |
| MIL/Mil | Military |
| MILCAP | Military Civic Action Program |
| MILCON | Military Construction |
| MILHLAP | Military Public Health Assistance Program |
| Military Civic Action | Civic action performed or supported by military or paramilitary forces using their military skills, equipment and resources in cooperation or on behalf of host government civil authorites, agencies or groups. |
| Military Power | Maximum unaugmented thrust condition of engine. |
| Military Unit Team | US military representatives assigned to advise and assist RVNAF regular units as opposed to US representatives assigned to further US-GVN objectives at subnational levels. |
| MILPHAP | Military Provincial Hospital Augmentation Program (Changed Oct 66 to Military Provincial Health Assistance Program). |
| MILREP | Military Report |
| MILSTAMP | Military Standard Transportation and Movement Procedures |
| MILSTD | Military Standard |
| MILSTRIP | Military Standard Requisition and Issue Procedures |
| MIMEX | Major Items Map Excess |
| MINI-NIOTC | Miniature Naval Inshore Operations Training Center |
| MINRON | Mine Squadron |
| MIO | Military Intelligence Office |
| MIP | Motivation Indoctrination Program |
| MIS | Military Intelligence Service |
| MISC | Mobile Infiltration Surveillance Center |
| Missile Free | Authority is granted to fire unless target is identified as friendly. |
| Missile Tone | Audio signal indicating AIM-9 is locked on to an IR source. |
| MIUW | Mobile Inshore Undersea Warfare |
| MIUWG | Mobile Inshore Undersea Warfare Group |
| MIUWSU | Mobile Inshore Undersea Warfare Surveillance Unit |
| Mk/MK | Mark |
| MLG | Mission Liaison Group |
| MLGROCV | Military Advisory Group, Government of the Republic of China |
| MLMS | Motor Launch Minesweeper |
| MLO | Military Liaison Office/Officer |
| MM | Messagerie Maritimes (piers) |
| mm/MM | Millimeter(s) |
| MMASF | Military Mutual Aid and Savings Fund |
| MMC | Medium Maintenance Center/Material Management Center |
| MMD | Merchant Marine Detail |
| MMIP | Marine Modernization and Improvement Plan |
| MMS | Military Medical Schcol |
| MND | Ministry of National Defense |
| MNK | Marine Nationale Khmer (Cambodian/Khmer Navy) |
| MOAT | Mobile Operational Advisory Team |
| MOB | Military Operational Boundary |
| Mobile Action Cadre | The New Life pacification cadre who replaced the Strategic Hamlet Construction cadres in 1964. |
| MOD | Ministry of Defense |
| MOD&WV | Minstry of Defense and War Veterans |
| MOE | Ministry of Education |
| MOF | Ministry of Finance |
| MOFA | Minister of Financial Affairs |
| MOGAS | Motor Gasoline |
| MOH | Minister/Ministry of Health |
| MOI | Methods of Instruction |
| MOI | Minster/Ministry of Information (GVN) |
| MOL | Ministry of Labor |
| MON | Monitor |
| MOND | Ministry of National Defense |
| MONEVAL | Monthly Evaluation Report (Hqs USMACV) |
| MOOSE | Move out of Saigon Expeditiously (Project) |
| MOP | Measurement of Progress |
| MORD | Ministry of Revolutionary/Rural Development |
| MOS | Military Occupational Specialty |
| MOTU | Mobile Ordnance Training Unit |
| MP | Military Police |
| MPA | Military Personnel Army |
| MPC | Military Payment Certificate |
| MPC | Mission Press Center |
| MPCC | Medical Policy Coordinating Committee |
| MPCO | Military Property and Construction Office |
| MPPCO | Military Property Construction Office |
| MPS | Ministry of Public Security (NVN) |
| MPW | Ministry of Public Works |
| MR | Military Region(s) |
| MRB | Mobile Riverine Base |
| MRC | Mobile Riverine Command |
| MRD | Ministry of Revolutionary Development |
| MRF | Mobile Riverine Force |
| MRMC | Maintenance Repair & Minor Construction Program |
| MRO | Manual/Materiel Release Order |
| MRS | Military Railway Service |
| MRT | Military Rated Thrust - see military power |
| MRTT | Military Region Tri-Thien |
| MRTTH | Military Region Tri Thien Hue |
| MS | Master of Science |
| MSB | Minesweeping Boat |
| MSC | Military Sealift Command |
| MSC | Minesweeper Coastal |
| MSD | Military Security Department |
| MSD | Minesweeper Drone |
| MSF | Mobile Strike Force |
| MSG | Message |
| MSGT | Master Sergeant |
| MSL | Mean Sea Level. Altitude reference. |
| MSM | Meritorious Service Medal |
| MSM | Minesweeper, Mechanized |
| MSM | Minesweeper, River (Converted LCM-6) |
| MSO | Military Security Office (COSVN) |
| MSO | Minesweeper, Ocean |
| MSP | Minesweeping Patrol |
| MSQ | Mobile Search Special (radar for ground-directed bombing) |
| MSR | Minesweeper, River |
| MSRCO | Master Ship Repair Contract Office |
| MSS | Malayan Security Service |
| MSS | Military Security Service |
| MSTS | Military Sea Transport Service |
| MSTSFE | Military Sea Transport Service, Far East |
| MSW | Ministry of Social Welfare |
| MSWR | Ministry of Social Welfare Refugees |
| MT | Metric/Measurement Ton |
| MT&P | Ministry of Transportation & Post |
| MTC | Marine Training Center |
| MTC | Mine Training Center |
| MTD | Mobile Training Detachment |
| MTDA | Modified Table of Distribution & Allowance |
| MTDS | Marine Tactical Data System |
| MTMTS | Military Transport Management Terminal Service |
| MTN | Military Telecommunications System |
| MTN-V | Military Telecommunication Network Vietnam |
| MTNV | Military Telecommunications Network-Vietnam |
| MTOE | Modified Table of Organization & Equipment |
| MTON | Metric Ton |
| MTS | Military Telecommunications System |
| MTS | Mobile Training Set |
| MTT | Mobile Training Team(s) |
| MTVN | Military Telecommunications Network-Vietnam |
| MVA | Ministry of Veterans Affairs |
| MWA | Military Working Arrangement |
| MWV | Ministry of War Veterans |