Brett Petersen (born 9 September 1976) is a South African former swimmer, who specialised in breaststroke events. He won a gold medal in the 100 m breaststroke at the 1999 All-Africa Games, and later became a top 8 finalist in the same distance at the 2000 Summer Olympics. While studying in the United States, Petersen was part of the 200-yard medley relay team that claimed a top finish at the 1998 Atlantic Coast Conference Swimming Championships. Petersen also played for the Florida State Seminoles swimming and diving team under head coach Neil Harper, and later became a graduate of management information systems at the Florida State University in Tallahassee, Florida.