The Tank, Cruiser, Mk VI or A15 Crusader was one of the primary British cruiser tanks of the early part Second World War and perhaps the most important British tank of the North African Campaign. The Crusader's mobility made it a favourite of British tank crews and its Ordnance QF 6 pounder main gun made it more than a match for the early Panzer III and Panzer IV tanks it faced in combat. By late 1942, the limited diameter of its turret ring prevented further armament upgrades and this, combined with the presence of Tiger I Tanks among the Afrika Korps and overheating problems caused by the high temperatures of the desert, led to the design being phased out in favour of the new US built Sherman III medium tank and the British Cromwell heavy cruiser.

In 1938, Nuffield Mechanization & Aero Limited produced their A16 design for a heavy cruiser tank based on Christie suspension. Looking for a lighter and cheaper tank to build, the General Staff requested alternatives. To this end the A13 Mk III cruiser tank design which would enter service as the "Tank, Cruiser Mk V" and known in service as "Covenanter" was designed. Nuffield were, in 1939, offered the opportunity to take part in the production of Covenanter. Nuffield, however, preferred to work on its own version of the A13—though they still provided design work for the Covenanter's turret. This new tank was adopted as "Tank, Cruiser, Mk VI Crusader", under General Staff specification A15. Although Crusader is often referred to as an improved version of the Covenanter, in fact it was a parallel design.