Alvin Nugent (Bo) McMillin (January 12, 1895 – March 31, 1952) was an American football player and coach at the collegiate and professional level. He played college football at Centre College in Danville, Kentucky, where he was a three-time All-American at quarterback, and led the Centre Praying Colonels to an upset victory over Harvard in 1921. McMillin was inducted into the College Football Hall of Fame as a player as part of its inaugural 1951 class.
McMillin was 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. In 1945, he led Indiana to its first Big Ten Conference title and was named AFCA Coach of the Year.
After graduating from Centre, McMillin played professionally with the Milwaukee Badgers and Cleveland Indians—two early National Football League (NFL) teams—in 1922 and 1923. He later 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 his death. McMillin's career NFL coaching mark was 14–24.