A tank destroyer, tank hunter, tank killer, or self-propelled anti-tank gun is a type of armoured fighting vehicle, armed with a direct fire artillery gun or missile launcher, designed specifically to engage and destroy enemy tanks, often with limited operational capacities.

While tanks are designed for front-line combat, combining operational mobility and tactical offensive and defensive capabilities and performing all primary tasks of the armoured troops, the tank destroyer is specifically designed to take on enemy tanks and other armoured fighting vehicles. Many are based on a tracked tank chassis, while others are wheeled.

Since World War II, gun-armed powerful tank destroyers have fallen out of favor as armies have favored multirole main battle tanks. However, lightly armoured anti-tank guided missile (ATGM) carriers are commonly used for supplementary long-range anti-tank work. The resurgence of expeditionary warfare in the first two decades of the 21st century has seen the emergence of gun-armed wheeled vehicles, sometimes called "protected gun systems", which may bear a superficial resemblance to tank destroyers, but are employed as direct fire support units typically providing support in low-intensity operations such as the wars in Iraq and Afghanistan.