Thornton Willis (born May 25, 1936) is an American abstract painter. He has contributed to the New York School of painting since the late 1960s. Viewed as a member of the Third Generation of American Abstract Expressionists, his work is associated with Abstract Expressionism, Lyrical Abstraction, Process Art, Postminimalism, Bio-morphic Cubism (a term he coined) and Color Field painting.