A main battle tank (MBT), also known as a battle tank or universal tank, is a tank that fills the heavy direct fire role of many modern armies. They were originally conceived to replace the light, medium, heavy and super-heavy tanks. Development was spurred onwards in the Cold War with the development of lightweight composite armor. They are still supplemented in some armies with light tanks.

Today, main battle tanks are considered a key component of modern armies. Modern MBTs seldom operate alone, as they are organized into armored units which involve the support of infantry, who may accompany the MBTs in infantry fighting vehicles. They are also often supported by surveillance or ground-attack aircraft.