John LeRoy Christiansen (December 20, 1928 – June 29, 1986) was an American football player and coach.
He played professional football in the National Football League (NFL) for the Detroit Lions as a defensive back and return specialist from 1951 to 1958.
He helped lead the Lions to three NFL championships in 1952, 1953, and 1957 and was a first-team All-NFL player in six of his eight years in the league.
He led the NFL in interceptions in 1953 and 1957 and in punt returns for touchdown in 1951, 1952, 1954, and 1956.
His eight career punt returns for touchdowns was an NFL record until 1989 and remains the fourth best in league history.
He was inducted into the Pro Football Hall of Fame in 1970.After retiring as a player, Christiansen served as a football coach for 25 years from 1959 to 1983, including stints as the head coach of the San Francisco 49ers, compiling a 26–38–3 record from 1963 to 1967, and at Stanford, where he compiled a 30–22–3 record from 1972 to 1976.
He concluded his career as an assistant coach for the Kansas City Chiefs (1977), Seattle Seahawks (1978–1982), and Atlanta Falcons (1983).