The Churchill (A22) was the last and heaviest of British infantry tanks and the one to see the most widespread use during World War II. It was also the first British tank developed during the war, a process that was sped up considerably (barely 11 months between conception and the first production units built) after the loss of most heavy equipment during the Dunkirk evacuation. The Churchill had a characteristically long and narrow hull, reminiscent of World War I rhomboidal tanks, but with a low profile and the thickest armor fitted on a British tank (over 100 mm at the front). It featured some mechanical innovations including regenerative steering as well as hydraulically assisted controls and clutch, and its 11 small wheels on separate vertical coil springs allowed it to continue running even if some were lost. Unfortunately, it was quite slow and chronically under-gunned; initially with a feeble 2-pounder, later to a 6-pounder, and finally with a 75-mm gun, the same fitted on the US Sherman. This was still insufficient against most late-war German tanks although survivability was offset thanks to its thick armor. Churchills saw combat in most fronts during the mid- and late-war years, initially in the failed Dieppe Raid of 1942, later in the Battle of El Alamein before more widespread service in Italy and Northwest Europe. The Churchill also proved to be an excellent platform for support roles, many which included specialized vehicles for Hobart's Funnies. Still in British service in the 1950s, it saw limited action during the early part of the Korean War as well. Other users included Commonwealth and Polish armies, as well as the USSR and (post-war) Ireland.

The initial A20 prototypes (completed in September 1940) were designed as a replacement for the Matilda II but development soon switched to the A22 Infantry Tank Churchill. The Churchill Mk. I was armed with a 2-pounder gun a 3-in howitzer mounted in the bow for infantry support, and was used initially during the Dieppe Raid. This was followed by the Mk. II which removed the howizer, although this was reinstated in the Mk. II CS which swapped the position of the two guns compared to the Mk. I. and the Mk. IICS with same howitzer plus the 2-pounder in the nose. Many of these were later fitted with full track covers. The Mk. III was the first to be equipped with the 6-pounder gun in a new welded turret (some Mk. I and IIs were also brought to this standard), while the Mk. IV had a cast turret and was otherwise identical to the Mk. III. The Mk. IV (NA 75) was the first to be fitted with 75-mm guns salvaged from wrecked Shermans. At the same time, while a British-produced variant of the 75-mm gun was later used on the Mk. VI. Addition of extra armor and a new cast/welded turret with a cupola (the first in a British tank) resulted in the Mk. VII (A22F) and was the main variant used in Northwest Europe as well as post-war, when it was redesignated A42. Final variants were mostly re-worked from earlier versions and included the Mk. IX (from the Mk. III or IV), the Mk. X (Mk. VI), and Mk. XI (Mk. V) which also had appliqué armor. Those that retained the original 6-pounder turret had the suffix LT. Churchills fitted with a 95-mm howitzers and used for close support included the Mk. V and Mk. VIII. Other variants included the Churchill Oke and Crocodile flamethrower, Churchill AVRE (Armoured Vehicle Royal Engineers), Churchill ARV (Armoured Repair Vehicle), and Churchill BARV (Beach Armoured Repair Vehicle). Bridging vehicles included the Churchill Ark family. Numerous other experimental support variants were developed and produced in small numbers.