The Military Medal (MM) was a military decoration awarded to personnel of the British Army and other arms of the armed forces, and to personnel of other Commonwealth countries, below commissioned rank, for bravery in battle on land. The award was established in 1916, with retrospective application to 1914, and was awarded to other ranks for "acts of gallantry and devotion to duty under fire". The award was discontinued in 1993, when it was replaced by the Military Cross, which was extended to all ranks, while other Commonwealth nations instituted their own award systems in the post war period.

The Military Medal was established on 25 March 1916. It was awarded to other ranks including non-commissioned officers and warrant officers, and ranked below the Distinguished Conduct Medal (DCM). Awards to British and Commonwealth forces were announced in the London Gazette, but not honorary awards to allied forces. (Lists of awards to allied forces were published by The National Archives in 2018 and are kept in country specific files within WO 388/6.)

When the medal was first introduced, it was unpopular among regular soldiers. MM and DCM recipient Frank Richards wrote that "the Military Medal without a shadow of a doubt had been introduced to save awarding too many DCMs. The old regular soldiers thought very little of the new decoration". Both the DCM and the MM attracted a gratuity and the decoration allowance of an extra sixpence a day to veterans with a disability pension. However, the allowance was only awarded once even if the recipient was awarded more than one gallantry award. The ratio in the First World War was approximately five MMs awarded for every DCM.

From September 1916 members of the Royal Naval Division, serving on Western Front alongside the Army, were made eligible for military decorations, including the Military Medal, for the war's duration. It could also be awarded to members of the Royal Air Force for gallant service on the ground.

Eligibility for the MM was extended, by a Royal Warrant dated 21 June 1916, to women whether British subjects or foreign, with the first awards gazetted on 1 September 1916. Although nurses of the Queen Alexandra's Imperial Military Nursing Service (QAIMNS) and the Territorial Force Nursing Service (TFNS) and other women serving with the British Army often had the social status of officers, they did not hold an officer's commission and were therefore ineligible for the Military Cross, but could be and were awarded the MM. Louisa Nolan, a civilian during the Easter Rising in Dublin, was awarded the Military Medal for her courage under fire in providing humanitarian aid to the wounded.

Since 1918 recipients of the Military Medal have been entitled to the post-nominal letters "MM".

Eligibility was extended to soldiers of the Indian Army in 1944.

The Military Medal was discontinued in 1993, as part of the review of the British honours system, which recommended removing distinctions of rank in respect of awards for bravery. Since then the Military Cross, previously only open to Commissioned and Warrant Officers, has been awarded to all ranks. The MM had also been awarded by Commonwealth countries but by the 1990s most, including Canada, Australia and New Zealand, were establishing their own honours systems and no longer recommended British honours.