A cloth diaper (American English) or a cloth nappy (Australian English and British English), also known as reusable diaper or reusable nappy, is a diaper made from textiles such as natural fibers, human-made materials, or a combination of both. Cloth diapers are in contrast to disposable diapers, made from synthetic fibers and plastics. They are often made from industrial cotton which may be bleached white or left the fiber’s natural color. Other natural fiber cloth materials include wool, bamboo, and unbleached hemp. Human-made materials such as an internal absorbent layer of microfiber toweling or an external waterproof layer of polyurethane laminate (PUL) may be used. Polyester fabrics microfleece or suedecloth are often used inside cloth diapers as a "stay-dry" wicking liner because of the non-absorbent properties of those synthetic fibers.

Modern cloth diapers come in a host of shapes, including preformed cloth diapers, all-in-one diapers with waterproof exteriors, fitted diaper with covers and pocket or "stuffable" diapers, which consist of a water-resistant outer shell sewn with an opening for insertion of absorbent material inserts.