HMS M31

{{Short description|M29-class monitor}}

{{Use dmy dates|date=December 2016}}

{{Use British English|date=December 2016}}

{{Infobox ship begin}} {{Infobox ship image |Ship image='M.31' in the Mediterranean RMG PU6337.jpg |Ship caption=Painting of M31 in 1916 }} {{Infobox ship career |Hide header= |Ship country=United Kingdom |Ship flag={{shipboxflag|United Kingdom|naval}} |Ship name=HMS M31 |Ship namesake= |Ship ordered=15 March 1915 |Ship builder=Harland & Wolff, Belfast |Ship yard number=487 |Ship laid down=March 1915 |Ship launched=24 June 1915 |Ship completed=9 July 1915 |Ship acquired= |Ship commissioned= |Ship decommissioned= |Ship in service= |Ship out of service= |Ship struck= |Ship reinstated= |Ship honours= |Ship fate=Sold 1948 and broken up at Llanelly |Ship notes= }} {{Infobox ship characteristics |Hide header= |Header caption= |Ship class=M29-class monitor |Ship displacement=580 tons deep load |Ship length={{convert|177|ft|3|in|m|abbr=on}} |Ship beam={{convert|31|ft|m|abbr=on}} |Ship draught={{convert|5|ft|11|in|m|abbr=on}} |Ship draft= |Ship propulsion=Triple expansion. Twin screws. Yarrow oil fuel 45 tons boilers. 400 hp (300 kW) |Ship speed=10 knots (19 km/h) |Ship range= |Ship complement=72 |Ship sensors= |Ship EW= |Ship armament=*2 × BL 6 in (152 mm) Mk XII guns 1 × 6-pounder AA |Ship armour=6 inches on gun shield |Ship armor= |Ship aircraft= |Ship notes= }}

HMS M31 was an M29-class monitor of the Royal Navy.

The availability of ten 6 inch Mk XII guns from the Queen Elizabeth-class battleships in 1915 prompted the Admiralty to order five scaled down versions of the M15-class monitors, which had been designed to utilise 9.2 inch guns. HMS M31 and her sisters were ordered from Harland & Wolff, Belfast in March 1915. Launched on 24 June 1915, she was completed in July 1915. Upon completion, HMS M31 was sent to the Mediterranean, and remained there until March, 1919.

In 1916, she defended the port city of Yanbo, in Saudi Arabia, against the Turkish army by providing artillery cover for the Arab rebels.{{cite book |last1=Lawrence |first1=T.E. |title=Seven Pillars of Wisdom |url=https://archive.org/details/sevenpillarsofwi00lawr |url-access=registration |date=1935 |publisher=Doubleday, Doran & Company, Inc. |location=Garden City |pages=[https://archive.org/details/sevenpillarsofwi00lawr/page/129 129-130]}} She served from May to September 1919 in support of British and White Russian forces in the White Sea, before returning to England.

In September 1923, HMS M31 was taken in hand for conversion to a minelayer. Equipped to carry 52 mines, she was renamed HMS Melpomene in December 1925. She was assigned to HMS Defiance the Torpedo School at Devonport. In September, 1939 she was converted to a torpedo training vessel, fitted with one 21 inch torpedo tube on the forecastle.

She was renamed HMS Menelaus in 1941, and was finally sold in 1948 and broken up at Llanelly.