Frank Seiler Butterworth Sr. (September 21, 1870 – August 21, 1950)[1] was an American college football player and coach.

[2] After his college career was over, Butterworth coached football at the University of California, Berkeley (1895–1896) and Yale (1897–1898).

[3] The 1897 Yale football team coached by Butterworth went undefeated with two ties, against Army and Harvard.

He served as a Connecticut State Senator from 1907 to 1909 and was a Second Lieutenant in the Chemical Warfare Service during World War I.

This biographical article relating to a college football coach first appointed in the 1890s is a stub.