- M&A Mergers & Acquisitions
- MAC Media Access Control / Medium Access Control
- MADN Multiple Appearance Directory Number
- MAN Metropolitan Area Network
- MAP Manufacturing Automation Protocol
- MAPI Microsoft Mail Application Programming Interface
- MARC MAchine Readable Cataloging
- MAU Multistation Access Units
- MB MegaByte
- MBASIC Microsoft BASIC
- Mbps Mega bits per second
- MCA Micro Channel Architecture
- MCGA Monochrome Graphics Adapter
- MCI Media Command Interface / Media Control Interface
- MCS Microsoft Consulting Services
- MD Make Directory
- MDA Monochrome Display Adapter
- MDI Multiple Document Interface
- MEPS Multi-language Electronic Phototypesetting System
- MFC Microsoft Foundation Classes
- MFF MIDI File Format
- MFM Modified Frequency Modulation
- MHS Message Handling Service
- MHz MegaHerz
- MIB Management Information Base
- MIDI Musical Instrument Digital Interface
- MILNET MILitary NETwork
- MIME Multipurpose Internet Mail Extensions
- MIPS Million Instructions Per Second
- MIS Management Information Systems
- MLID Multiple Link Interface Driver
- MMAC Multi Media Access Center
- MMM Multiple Master Metrics
- MMU Memory Management Unit
- MNP Microcom Networking Protocol
- MO Magnetic Orientation / Magneto-Optical
- MODEM MOdulation DEModulation
- MOM Message-Oriented Middleware
- MOMspider Multi-Owner Maintenance spider
- MOO MUD Oriented Objects
- MOP Maintenance Operations Protocol
- MOS Mass Optical Storage / Metal Oxide Semiconductor
- MOST Mass Optical Storage Technologies
- MP/M MultiProgram monitor for Microcomputers
- MPC Multimedia PC
- MPEG Motion Picture Experts Group
- MPP Massively Parallel Processing
- MPU MicroProcessor Unit
- MR Modem Ready
- MRBC Multiple-Resolution Bitmap Compiler
- ms millisecond
- MS-BASIC MicroSoft BASIC
- MS-DOS MicroSoft DOS
- MSAU MultiStation Access Unit
- MSB Most Significant Byte
- MSDN MicroSoft Developer Network
- MSI Medium Scale Integration
- MSN MicroSoft Network
- MSP Master Stack Pointer
- MSRP Manufacturer's Suggested Retail Price
- MTA Message Transfer Agent
- MTBF Mean Time Between Failures
- MTF Modular Transfer Function
- MTTR Mean Time To Repair
- MTU Maximum Transmission Unit
- MUD Multi-User Dungeon / Multi-User Dimension / Multi-User Dialogue / Multi-User Domain
- MULTICS MULTI-User Interactive Computer System / MULTIplexed Information and Computing Service
- MUNG Mung Until No Good
- MUSE Multi-User Simulation Environment
- MUSH Multi-User Shared Hallucination
- MUSIC MUlti Session In Community
- MUX MUltipleX, MUltipleXor
- MVC Model-View-Controller
- MVDMS Multiple Virtual DOS Machines
- MVL Multi-Valued Logic
- MVP Multimedia Video Processor
- MVS Multiple Virtual Storage
- MX Mail EXchange Record