The Conspicuous Gallantry Medal (CGM) was, until 1993, a military decoration for gallantry in action. Initially, it was awarded to petty officers and seamen of the Royal Navy, including Warrant Officers and other ranks of the Royal Marines. The CGM was also later awarded to personnel of other Commonwealth navies. From 1943, it was also awarded to NCOs of the Royal Air Force and other Commonwealth air forces, for conspicuous gallantry in action against the enemy in the air. The CGM was officially discontinued in 1993.

The Conspicuous Gallantry Medal was the second level bravery award for ratings of the Royal Navy, ranking below the Victoria Cross and, after its institution in 1914, above the Distinguished Service Medal. It was normally awarded with an annuity or gratuity. In 1943, during the Second World War, a Royal Air Force version, the Conspicuous Gallantry Medal (Flying), was added. Since 1917, recipients have been entitled to use the post-nominal letters "CGM".

The original Royal Navy medal was instituted in 1855 to recognise gallantry during the Crimean War, as the Naval counterpart of the Distinguished Conduct Medal. Only twelve were finally awarded, with the medals created by adapting existing examples of the Royal Marines Meritorious Service Medal, with the words 'MERITORIOUS SERVICE' erased from the reverse inscription, and 'CONSPICUOUS GALLANTRY' engraved in its place.

The Conspicuous Gallantry Medal was re-instituted on 7 July 1874 as a permanent decoration, and was initially used to reward gallantry in the various colonial campaigns of the late nineteenth century in which the Royal Navy took part.

It remained an exclusively Naval award until World War II when a number of changes were made. Eligibility was extended in April 1940 to Royal Air Force personnel serving with the Fleet; in July 1942 to Army personnel serving afloat, for example manning a merchant ship's anti-aircraft guns; and in September 1942 to ratings of the Merchant Navy.

In January 1943 the Conspicuous Gallantry Medal (Flying) was established for acts of conspicuous gallantry whilst flying in active operations against the enemy, of a standard below that required for the Victoria Cross, but above that for the Distinguished Flying Medal.

In 1979 eligibility for a number of British awards, including the CGM, was extended to permit posthumous awards. Until that time, only the Victoria Cross and a mention in dispatches could be awarded posthumously.

In 1993, the Conspicuous Gallantry Medal, Distinguished Service Order (when awarded specifically for gallantry) and Distinguished Conduct Medal were all replaced by the Conspicuous Gallantry Cross (CGC). The CGC is tri-service and is awarded to all ranks. It is second only to the Victoria Cross for bravery in action.