M
| Class | Country | Type | Launch years | Displacement (tons) | Number |
| M = Marcilio Dias | Brazil | destroyer | 1940-41 | 1,500 | 3 |
| Mackerel | US | submarine | 825 | 2 | |
| Mahan | US | destroyer | 1935-36 | 1,488 | 18 |
| Manxman = Abdiel | UK | minelayer | 1940-44 | 2,650 | 6 |
| Marasti | Romania | destroyer | 1917-18 | 1,610 | 2 (2 retained by Italy) |
| Marcilio Dias = M | Brazil | destroyer | 1940-41 | 1,500 | 3 |
| Matsu | Japan | destroyer escort | 1944 | 1,262 | 18 |
| Maxim Gorkiy (Project 26-bis): sub-class of Kirov | USSR | heavy cruiser | 1938-44 | 8,048 | 4 |
| Minekaze | Japan | destroyer | 1919-22 | 1,345 | 13 |
| Minotaur | UK | light cruiser | 1943-45 | 8,800 | 8 6 completed |
| Mirabello | Italy | destroyer | 1915-16 | 1,811 | 2 |
| Mississippi | Greece | battleship | 1905 | 13,000 | 2 |
| Mogador = 2930 tonnes | France | destroyer (or light cruiser) | 1936-37 | 2,884 | 2 completed |
| Mogami | Japan | heavy cruiser | 1934-36 | 8,500 | 4 |
| Momi | Japan | Destroyer | 1918-23 | 770 | 21 |
| Momo | Japan | Destroyer | 1917-18 | 835 | 4 |
| Mutsuki | Japan | destroyer | 1925-27 | 1,315 | 12 |
| Myōkō | Japan | heavy cruiser | 1927-28 | 10,000 | 4 |
Read more about this topic: List Of World War II Ship Classes