William Willet (November 1, 1869 – March 29, 1921) was an American portrait painter, muralist, stained glass designer, studio owner and writer. An early proponent of the Gothic Revival and active in the "Early School" of American stained glass, he founded the Willet Stained Glass and Decorating Company, a stained glass studio, with his wife and partner Anne Lee Willet, in protest against the opalescent pictorial windows which were the rage at the turn of the twentieth century.