Clark Daniel Shaughnessy (originally O'Shaughnessy) (March 6, 1892 – May 15, 1970) was an American football coach and innovator. He is sometimes called the "father of the T formation" and the original founder of the forward pass, although that system had previously been used as early as the 1880s. Shaughnessy did, however, modernize the obsolescent T formation to make it once again relevant in the sport, particularly for the quarterback and the receiver positions. He employed his innovations most famously on offense, but on the defensive side of the ball as well, and he earned a reputation as a ceaseless experimenter.