A motorcycle trunk is a storage compartment in the vicinity of the seat, often complimenting panniers or saddlebags. A trunk mounted above and to the rear of the seat may be called a top box or a top case. Some are fitted with electric lighting systems for enhanced safety, and a backrest for a passenger. Trunk may also refer to the under-seat storage space built into a motorcycle or scooter.
Harley-Davidson riders often call a Harley's trunk a "tour pack".