Water polo player Rainer Osselmann represented West Germany at the 1984 Los Angeles and 1988 Seoul Olympics. In 1984 the team won the bronze medal and in 1988 finished fourth, losing the bronze medal match 14-13 against the Soviet Union. In 1985 Osselmann won a bronze medal at the European Championships and also won the World Cup. In 1981 and 1989, he won the European titles.
Nationally, Osselmann played with ASC Duisburg, helping them win the German Cup in 1989. After his active career, he became sports director at his home club, and CEO of a software company in Duisburg. His parents Birgit Klomp and Friedhelm Osselmann were also Olympians.