A tank is a large, heavily armoured fighting vehicle with tracks and a large tank gun that is designed for front-line combat. Modern tanks are mobile land weapon platforms, mounting a large-calibre cannon in a rotating gun turret. They combine this with heavy vehicle armour which provides protection for the crew, the vehicle's weapons, and its propulsion systems, and operational mobility, due to its use of tracks rather than wheels, which allows the tank to move over rugged terrain and be positioned on the battlefield in advantageous locations. These features enable the tank to perform well in a tactical situation: the combination of powerful weapons fire from their tank gun and their ability to resist enemy fire means the tank can take hold of and control an area and prevent other enemy vehicles from advancing. In both offensive and defensive roles, they are powerful units able to perform key primary tasks required of armoured units on the battlefield. The modern tank was the result of a century of development from the first primitive armoured vehicles, due to improvements in technology such as the internal combustion engine, which allowed the rapid movement of heavy armoured vehicles. As a result of these advances, tanks underwent tremendous shifts in capability during the World Wars of the 20th century.

A tank is an armoured combat vehicle. The other common meaning is a storage tank, a container, usually for liquids.