The Cromwell tank, officially Tank, Cruiser, Mk VIII, Cromwell (A27M), was one of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War-era military leader Oliver Cromwell, the Cromwell was the first tank put into service by the British to combine high speed from a powerful, reliable engine and reasonable armour. The intended dual-purpose high velocity gun could not be fitted in the turret, so a medium velocity dual purpose gun was fitted instead. Further development of the Cromwell combined with a high velocity gun led to the Comet tank.

The cruiser tank was a British tank concept of the interwar period for tanks designed as modernised armoured and mechanised cavalry, as distinguished from infantry tanks. Cruiser tanks were developed after medium tank designs of the 1930s failed to satisfy the Royal Armoured Corps. The cruiser tank concept was conceived by Giffard Le Quesne Martel, who preferred many small light tanks to swarm an opponent, instead of a few expensive and unsatisfactory medium tanks. "Light" cruiser tanks carried less armour and were correspondingly faster, whilst "heavy" cruiser tanks had more armour and were slightly slower.