| Birth Place: | Darmstadt, Germany |
| Height: | 1.85m (06.07feet) |
| Weight: | 800NaN0 |
| Sport: | Swimming |
| Club: | DSW 1912, Darmstadt |
| Show-Medals: | yes |
Hans-Joachim Klein (pronounced as /de/; born 20 August 1942) is a retired West German freestyle swimmer. He competed in various freestyle sprint events at the 1960 and 1964 Olympics and won three silver and one bronze medals in 1964. In 1965 he was elected as German Sportspersonality of the Year.
In 1962–1963 Klein studied industrial engineering at the University of Southern California. He later defended a PhD in Germany and went into politics and administration. In 1969–1985 he worked at the Hessian Economic and Traffic Ministry, between 1985 and 1997 was a Darmstadt District Administrator, and from 1997 until his retirement in 2008 was the manager of the Supply and Transport Company of Leipzig. In addition, in 2001–2007 he acted as president of the German Olympic Society.