A quarter panel (British English: rear wing) is the body panel (exterior surface) of an automobile between a rear door (or only door on each side for two-door models) and the trunk (boot) and typically wraps around the wheel well.
The similar front section between the door and the hood (bonnet) is called a fender (front wing), and may sometimes also be referred to as a quarter panel.
A quarter panel is typically a welded-on component of the unibody structure.
Replacement of a sheet metal quarter panel typically requires it to be cut off the vehicle and a replacement part to be welded (or sometimes bonded) to the vehicle.
Due to the high amount of specialized labor, a quarter panel may often be repaired rather than replaced by hammering the damaged area to a relatively flat surface, and then applying a body filler to smooth out the damaged area to match the original surface.