A swim cap, swimming cap or bathing cap, is a silicone, latex or lycra cap worn on the head by recreational and competitive swimmers.

Caps are worn for various reasons. Some facilities require the wearing of swim caps, in order to protect filters from becoming clogged with loose hairs which fall from the scalp of swimmers who are not wearing a cap. Caps are also sometimes worn in an attempt to keep the hair relatively dry or free from chlorinated water, to keep the sun off of the hair, and also, when a cap is worn with ear plugs, in order to keep water out of the ears.

Competitive swim caps are made of tightly fitted silicone, latex, or lycra that hugs the skull of its user, providing cover for his or her hair. This reduces drag in the water caused by loose hair. During longer swimming sessions, a swim cap keeps the head warm.

Swim or SWIM may refer to:

A cap is a form of headgear. Caps have crowns that fit very close to the head and have no brim or only a visor. They are typically designed for warmth and, when including a visor, blocking sunlight from the eyes. They come in many shapes and sizes.