M class
- Abercrombie-class monitor
- Admiralty M-class destroyer
- British M-class submarine
- Class M (disambiguation)
- Karel Doorman-class frigate
- L and M-class destroyer
- M type (disambiguation)
- M-class Melbourne tram
- M-class Sydney tram
- M-class blimp
- M-class cruiser
- M-class destroyer
- M-class minesweeper
- M-class minesweeper (Germany)
- M-class minesweeper (Netherlands)
- M-class submarine
- M-segment
- Maersk M-class container ship
- Marcílio Dias-class destroyer
- Mercedes-Benz M-Class
- NZR M class
- OOCL M-class container ship
- Pennsylvania Railroad class M1
- United States M-class submarine
- Victorian Railways M class
- Victorian Railways M class (diesel-hydraulic)