William Thomas Brennan (October 25, 1880 – September 13, 1933) was an American Major League Baseball umpire and college football coach.

[3] In 1912, Philadelphia club owner Horace Fogel charged that Brennan and other umpires had treated his team unfairly in postseason play.

He was away from football for a few years before taking an assistant coaching position at Tulane University in 1919 under Clark Shaughnessy.

[6] He spent several seasons at Tulane and later coached at the University of Tennessee at Memphis and Little Rock Junior College.

[7] On Sunday, September 10, 1933, Brennan umpired the final game of the Southern Association season between Chattanooga and Knoxville.