The trunk (American English) or boot (British English) of a car is the vehicle's main storage or cargo compartment, often a hatch at the rear of the vehicle. It can also be called a tailgate.

In Indian English, the storage area is known as a dickey (also spelled dicky, dickie, or diggy). In Southeast Asia, it is known as a compartment.

The trunk or luggage compartment is most often at the rear of the vehicle. Early designs had an exterior rack on the rear of the vehicle to attach a luggage trunk. Later designs integrated the storage area into the vehicle's body, and eventually became more streamlined. The main storage compartment is normally provided at the end of the vehicle opposite to which the engine is located.

Some vehicles have the trunk in front of the passenger compartment, e.g. rear-engined cars like Volkswagen Beetle and Porsche 911, or electric vehicles like Ford F-150 Lightning. This is known as a frunk, a portmanteau of the words "front" and "trunk". The alternative term froot (a combination of "front" and "boot") is also occasionally used.

There are also vehicles with both front and rear trunks, either with low profile rear drivetrains, e.g. Volkswagen Type 3 or Tesla Model S, or with a mid-engine, e.g. Porsche 914 and Boxster, Toyota MR2 and Fiat X1/9.

Sometimes during the design life of the vehicle, the lid may be restyled to increase the size or improve the practicality and usefulness of the trunk's shape. Examples of this include the Beetle redesign to the 1970s 'Super Beetle' and the pre-war and 1950s post war Citroën Traction Avant.

The door or opening of a cargo area may be hinged at the top, side, or bottom.

If the door is hinged at the bottom it is called a tailgate, particularly in the United States. They are used on station wagons and pickup trucks, as well as on some sport utility vehicles (SUV). Traditional drop-down station wagon and pickup tailgates can also serve as a mount for a workbench.