A car bomb, bus bomb, van bomb, lorry bomb, or truck bomb, also known as a vehicle-borne improvised explosive device (VBIED), is an improvised explosive device designed to be detonated in an automobile or other vehicles.

Car bombs can be roughly divided into two main categories: those used primarily to kill the occupants of the vehicle (often as an assassination) and those used as a means to kill, injure or damage people and buildings outside the vehicle. The latter type may be parked (the vehicle disguising the bomb and allowing the bomber to get away), or the vehicle might be used to deliver the bomb (often as part of a suicide bombing).

It is commonly used as a weapon of terrorism or guerrilla warfare to kill people near the blast site or to damage buildings or other property. Car bombs act as their own delivery mechanisms and can carry a relatively large amount of explosives without attracting suspicion. In larger vehicles and trucks, weights of around 7,000 pounds (3,200 kg) or more have been used, for example, in the Oklahoma City bombing. Car bombs are activated in a variety of ways, including opening the vehicle's doors, starting the engine, remote detonation, depressing the accelerator or brake pedals or simply lighting a fuse or setting a timing device. The gasoline in the vehicle's fuel tank may make the explosion of the bomb more powerful by dispersing and igniting the fuel.