A swimsuit, bathing suit, or swimming costume is an item of clothing designed to be worn while engaging in a water-based activity or water sports, such as swimming, water polo, diving, surfing, water skiing, or during activities in the sun, such as sun bathing. A swimsuit can also be worn as an undergarment in sports that require a wetsuit such as water skiing, scuba diving, surfing, and wakeboarding. Swimsuits are also worn when there is a need to display the body, as in the case of beauty pageants or bodybuilding contests. Glamour photography and magazines like Sports Illustrated's annual "swimsuit issue" feature models and sports personalities in swimsuits.
There is a very wide range of styles of modern swimsuits, which vary in relation to body coverage and materials.