The Tank, Cruiser, Mk III, also known by its General Staff specification number A13 Mark I, was a British cruiser tank of the Second World War. It was the first British cruiser tank to use the Christie suspension system, which gave higher speeds and better cross-country performance; previous cruiser tank models had used triple wheeled bogie suspension.

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.