Louis Jean Pierre Vieillot (May 10, 1748 - 1831) was a French ornithologist.

Vieillot was one of the first ornithologists to study changes in plumage, and also one of the first to study live birds as well as skins. He described a large number of birds for the first time, especially those he encountered during the time he spent in the West Indies and North America.

Vieillot was born in Yvetôt . He was in business on the Caribbean island of San Domingo (Haiti), but was forced to flee to the United States during the French Revolution. He returned to France, where he wrote Histoire naturelle et générale des colibris, oiseaux-mouches, jacamars et promerops (1802) with Jean Baptiste Audebert and Ornithologie Française (1823-30). He also contributed to the Nouveau Dictionaire d'Histoire Naturelle (1803-19). He is believed to have died in poverty in Rouen.