A tank destroyer is a type of armored fighting vehicle armed with a gun or missile launcher, and is designed specifically to engage enemy armored vehicles. Many have been based on a tracked tank chassis, while others are wheeled.

Since World War II, main battle tanks have largely replaced gun-armed tank destroyers although lightly armored anti tank guided missile (ATGM) carriers are commonly used for supplementary long-range anti-tank work. However, the resurgence of expeditionary warfare in the past twenty years 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 Iraq and Afghanistan.

Dedicated anti-tank vehicles made their first major appearance in the Second World War as combatants developed effective armored vehicles and tactics. Some were little more than stopgap solutions, mounting a gun on a tracked vehicle to give mobility, while others were more sophisticated designs. An example of the development of tank destroyer technology throughout the war are the Marder III and Hetzer vehicle, that were very different in spite of being based on the same chassis: Marder was straightforwardly an anti-tank gun on tracks whereas Hetzer traded some firepower (its Pak 39, designed to operate within the confines of a full-armored fighting compartment, fires the same projectiles from a reduced propellant charge compared to Marder's Pak 40) for better armor protection and ease of battlefield concealment.