Hans-Joachim "HaJo" Geisler (born 27 May 1955) is a retired German swimmer who won a gold and a bronze medal at the 1975 World Aquatics Championships. He also competed at the 1972 and 1976 Summer Olympics. In 1972 his team finished fourth in the 4 × 200 m freestyle relay, 0.15 seconds short of a bronze medal. Between 1973 and 1978 he won eight national titles, including six in the 400 m individual medley event.