:"Rear end" redirects here but is also a name for the buttocks.
A rear-end collision (often called simply rear-end or in the UK a shunt) is a traffic accident wherein a vehicle (usually an automobile or a truck) crashes into the vehicle in front of it, so called because it hits its rear. It may also be a rail accident wherein a train runs into the rear of a preceding train.

Typical scenarios for rear-ends are a sudden deceleration by the first car (for example, to avoid someone crossing the street) the following car that does not have the time to brake and collides with the first at a road junction the following car accelerates more rapidly than the leading.

As a rule of thumb, crashing into another car is equivalent to crashing into a rigid surface (like a wall) at half of the speed. This means that rear-ending a still car while going at 30 mph is equivalent, in terms of forces, to crashing into a wall at 15 mph. The same is true for the vehicle crashed into.

A typical medical consequence of rear-ends, even in case of collisions at moderate speed, is whiplash. In more severe cases permanent injuries, e.g. herniation, may occur.

For purposes of insurance and policing, the driver of the car that rear-ends the other car is almost always considered to be at fault due to not being within stopping distance or lack of attention. An exception to this rule comes into play if the rear-ended vehicle is in reverse gear. If the driver of the car that was rear-ended files a claim against the driver who hit him, said driver could be responsible for all damages to the other driver's car.

The Ford Pinto became the focus widespread concern when it was alleged that a flaw in its design could cause fuel-fed fires as the result of a rear-end collision.

thumb|300px|A MINI Cooper'S before and after a high speed rear end impact