A notchback is a design of a car with the rearmost section that is distinct from the passenger compartment and where the back of the passenger compartment is at an angle to the top of what is typically the rear baggage compartment. Notchback cars have "a trunk whose lid forms a distinct deck." In profile view, the body has a step down from the roof with a downward inclined passenger compartment's rear window to meet an almost horizontal trunk lid extending to the rear of the car.

The category may be characterized as having a three-box design where the trunk volume is less pronounced than the engine and passenger compartments.

Many models of sedans, coupés, or hatchbacks could be classified as notchbacks. However, the category has limited salience outside of American car manufacturers distinguishing the three-box models from other body styles in the same model range. For example, the Chevrolet Vega range included both a notchback coupe and a fastback coupe.