Klaus Paul Alfred Clusius (19 March 1903 – 28 May 1963) was a German physical chemist from Breslau (Wroclaw), Silesia.
During World War II, he worked on the German nuclear energy project, also known as the Uranium Club; he worked on isotope separation techniques and heavy water production.
After the war, he was a professor of physical chemistry at the University of Zurich.