A crowbar is a tool consisting of a metal bar with a curved side and flattened extremities, often with a small fissure on one point. It is used as a lever to either force apart two objects or to remove nails. Crowbars are commonly used to open nailed wooden boxes.

Crowbars are 2^nd class levers.

Crowbar can also refer to an electrical circuit, usually used to prevent overvoltage from a power supply unit from damaging some downstream circuit. An electrical crowbar operates by throwing a short circuit across the voltage source, much as if one dropped its mechanical namesake across the output terminals of the power supply. Crowbar circuits are frequently implemented using an SCR (or thyratron) as the shorting device. Once triggered, they depend on the correct functioning of the power supply's current-limiting circuitry or, if that fails, the blowing of the line fuse or circuit breaker.

There are also two bands named Crowbar:

• Crowbar (US band)
• Crowbar (Canadian band)

In the computer game Half-Life, a crowbar is the basic melee weapon wielded by the player's character, Gordon Freeman. It became a popular symbol in the Half-Life fan culture.