A justacorps or justaucorps (/ˈʒuːstəkɔːr/) is a long, knee-length coat worn by men in the latter half of the 17th century and throughout the 18th century. The garment is of French origin, and was introduced in England as a component of a three-piece ensemble, which also included breeches and a long vest or waistcoat. This ensemble served as the prototype of the frock coat, which in turn evolved into the modern-day three-piece suit. The fabric selection and styling of the justacorps varied throughout time periods, as fashions frequently altered.