MMY or mmy may refer to:
- Mental Measurements Yearbook, an American non-fiction reference book
- MMY, the IATA code for Miyako Airport, Okinawa, Japan
- MMY, the Indian Railways station code for Marwar Mathania railway station, Rajasthan, India
- MMY, the Metro Trains station code for Montmorency railway station, Melbourne, Victoria, Australia
- MMY, the V/Line station code for Malmsbury railway station, Victoria, Australia
- mmy, the ISO 639-3 code for Migaama language, Chad