Cyrus Edgar Dietz (March 17, 1876 – September 13, 1929) was a justice of the Illinois Supreme Court and a college football player and coach. Dietz graduated in 1897 from the Grand Prairie Seminary in Onarga, Illinois. Dietz then attended Northwestern University, which was affiliated with the seminary. At Northwestern, Dietz played guard for four seasons for the football team, serving as captain of the team for the 1900 and 1901 seasons. Also starting on the team during three of these years was Dietz's brother, G. O. Dietz. Cyrus Dietz graduated from Northwestern in 1902 with a law degree, and was a member of the Delta Chi fraternity along with his brother.