Klaus Patau (1908–1975; born Klaus Pätau; pronounced [ˈklaʊs ˈpɛtaʊ]) was a German-born American geneticist. He received his PhD from the University of Berlin in 1936, worked from 1938 to 1939 in London, and then returned to Germany, where he worked at the Kaiser Wilhelm Institute for Biology until 1947. He emigrated to the United States in 1948 and obtained American citizenship. In 1960 he first reported the extra chromosome in trisomy 13. The syndrome caused by trisomy 13 is often called Patau syndrome. It is also known as Bartholin-Patau syndrome, since the clinical picture associated with trisomy 13 was described by Thomas Bartholin in 1656.
Patau was in the Department of Genetics at the University of Wisconsin–Madison, as was his wife and collaborator, the Finnish cytogeneticist Eeva Therman (1916–2004).