Alvin Nugent "Bo" McMillin (January 12, 1895 – March 31, 1952) was an American football player and coach, who served at both the collegiate and professional levels. He played college football at Centre College in Danville, Kentucky, where was a three-time All-American at quarterback, and led the Centre Praying Colonels to a historic upset victory over Harvard in 1921. After graduating from Centre, McMillin played professionally with the Milwaukee Badgers and Cleveland Indians, two early teams of the NFL, in 1922 and 1923.

McMillin served as the head football coach at Centenary College of Louisiana (1922–1924), Geneva College (1925–1927), Kansas State University (1928–1933), and Indiana University (1934–1947), compiling a career college football coaching record of 140–77–13. He then returned to the NFL, coaching the Detroit Lions from 1948 to 1950 and the Philadelphia Eagles for the first two games of the 1951 season before he succumbed to a fatal illness. His career NFL coaching mark was 14–24. McMillin's legendary "poor mouthing", pronounced in his distinctive Texas drawl, was in sharp contrast to his teams' successes. He was inducted into the College Football Hall of Fame as a player in 1951.