|Preceded by:||M15 class|
|Succeeded by:||Erebus class|
|Class and type:||Monitor|
|Length:||170 ft (52 m)|
|Beam:||31 ft (9.4 m)|
|Draught:||6 ft 9 in (2.06 m)|
|Speed:||10 knots (19 km/h)|
The ships of this class were ordered in March, 1915, as part of the Emergency War Programme of ship construction. The contract for construction was granted to Harland & Wolff, Belfast, who sub-contracted the construction of the M29 and M31 to Workman, Clark and Company.
The main armament of the ships, two 6-inch Mk XII guns, came from guns originally intended for the five Queen Elizabeth-class battleships which became surplus when their aft casemate mountings turned out to be unworkable and were dispensed with.
Ships of the class
- HMS M29 - launched on 22 May 1915 and later renamed Medusa and Talbot, she was sold in 1946.
- HMS M30 - launched on 23 June 1915, and sunk on 14 May 1916.
- HMS M31 - launched on 24 June 1915, and broken up for scrap in 1948.
- HMS M32 - launched on 22 May 1915, and sold in January 1920.
- HMS M33 - launched on 22 May 1915, is one of a number of World War I-era warships in existence today and is located in dry-dock near HMS Victory at Portsmouth Naval Base. It has been restored and is open to public.
- Colledge, J. J.; Warlow, Ben (2006) . Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
- Jane's Fighting Ships of World War One (1919), Jane's Publishing Company