The 1921 Centre vs. Harvard football game was a regular-season collegiate American football game played on October 29, 1921, at Harvard Stadium in Boston, Massachusetts. The contest featured the undefeated Centre Praying Colonels, representing Centre College, and the undefeated Harvard Crimson, representing Harvard University. Centre won the game 6–0, despite entering as heavy underdogs, leading to the game being widely viewed as one of the largest upsets in college football history. The game is often referred to by the shorthand C6H0; this originated shortly after the game when a Centre professor remarked that Harvard had been poisoned by this "impossible" chemical formula.

Robert T. Fisher was an American football player and coach. He played college football at Harvard University and was a consensus All-American in 1910 and 1911. He served as the head football coach at Harvard from 1919 to 1925, compiling a record of 43–14–5 and winning the 1920 Rose Bowl. His 1919 team was retroactively recognized as a national champion by a number of selectors. Fisher was one of the original trustees for the American Football Coaches Association (AFCA). He was inducted into the College Football Hall of Fame as a player in 1973.