A suit, lounge suit, or business suit is a set of clothes comprising a suit jacket and trousers of identical textiles worn with a collared dress shirt, necktie, and dress shoes.

A skirt suit is similar, but with a matching skirt instead of trousers. It is considered informal wear in Western dress codes. The lounge suit originated in 19th-century Britain as a more casual alternative for sportswear and British country clothing, with roots in early modern Western Europe. After replacing the black frock coat in the early 20th century as regular daywear, a sober one-colored suit became known as a lounge suit.