Ollan Conn Cassell (born October 5, 1937) is an American sprinter in the 1950s and 1960s, winning a gold medal in the men's 4 × 400 m relay at the 1964 Summer Olympics.

[1] Right now he serves as an adjunct professor for Olympic Sports history at the University of Indianapolis and is the president of the Indiana Olympian Association.

The following year, at the 1963 Pan American Games, Cassell won two gold medals in the relays and was second in 200 m and sixth in 100 m. At the Tokyo Olympics, Cassell was a semifinalist in 400 m and ran the opening leg in the American 4 × 400 m relay team, which won the gold medal with a new world record of 3:00.7.

After that, he retired from sports and started to work as the track and field administrator of the AAU 1965–1972.

He was elected to the United States National Track and Field Hall of Fame as a contributor in 2006.