A snap fastener (also called snap, popper, and press stud) is a pair of interlocking discs commonly used in place of buttons to fasten clothing. A circular lip under one disc fits into a groove on the top of the other, holding them fast until a certain amount of force is applied. Snap fasteners are often used in children's clothing, as they are relatively easy for children to use.

Snaps can be attached to fabric by hammering (using a specific punch and die set), plying, or sewing. For plying snap fasteners, there are special snap pliers.

In the famous Chinese Terracotta Army, dating from 210 BCE, the horse halters of wagons, made of a gold tube and a silver tube, were joined with a form of snap fasteners.^{[citation needed]}

Snap fasteners were first patented by German inventor Heribert Bauer^{[citation needed]} in 1885^{[citation needed]} as the "Federknopf-Verschluss"^{[citation needed]}, a novelty fastener for men's trousers. Some attribute the invention to Bertel Sanders, of Denmark. These first versions featured an S-shaped spring in the top disc instead of a groove. However, it wasn't until Jack Weil (1901-2008) modified the design and put snaps on his iconic Western shirts that the term "Snap" became commonplace and that snaps became of feature of much Western Wear.