The thong is a garment generally used as either underwear or as a swimsuit in some countries. It may also be worn for traditional ceremonies or competitions.

Viewed from the front, the thong typically resembles a bikini bottom, but at the back the material is reduced to a minimum. Thongs are almost always designed to cover the genitals, anus and perineum and leave part or most of the buttocks uncovered. The back of the garment typically consists of a thin waistband and a thin strip of material, designed to be worn between the buttocks, that connects the middle of the waistband with the bottom front of the garment. It is also used as a descriptive term in other types of garment, such as a bodysuit, bodystocking, leotard or one-piece swimsuit, with the meaning “thong-backed”.