MMO

MMO may refer to:

Entertainment

 * Massively multiplayer online game, a video game that can be played by many people simultaneously
 * Music Minus One, a record company in Westchester, New York

Science and technology

 * Methane monooxygenase, an enzyme
 * Maximum operating Mach number
 * Mercury Magnetospheric Orbiter, a component of the Mercury mapper BepiColombo
 * Mini-Mag Orion, a proposed type of spacecraft propulsion
 * Mixed metal oxide, a class of materials often used in electrodes

Other

 * Means, motive, and opportunity, the "indicators of suspicion"
 * Minimum municipal obligation, minimum contribution to a pension plan
 * Maio Airport, in Cape Verde, IATA code
 * Melton Mowbray railway station, England (National Rail station code MMO)
 * Marine Management Organisation, UK government body
 * Marine mammal observer, a professional in environmental consulting