M-class submarine

Two classes and a one-ship class of submarine are known as the M class


 * Soviet M-class submarine, a class of 148 Soviet Navy submarines built between 1933 and 1947
 * British M-class submarine, a class of 3 Royal Navy submarine monitors built in 1917 and 1918
 * USS M-1 (SS-47), a one-off United States submarine launched in 1915