Carl Friedrich Freiherr von Weizsäcker (28 June 1912 – 28 April 2007) was a German physicist and philosopher. He was the longest-living member of the team which performed nuclear research in Germany during the Second World War, under Werner Heisenberg‘s leadership. There is ongoing debate as to whether or not he and the other members of the team actively and willingly pursued the development of a nuclear bomb for Germany during this time.
A member of the prominent Weizsäcker family, he was son of the diplomat Ernst von Weizsäcker, elder brother of the former German President Richard von Weizsäcker, father of the physicist and environmental researcher Ernst Ulrich von Weizsäcker and father-in-law of the former General Secretary of the World Council of Churches, Konrad Raiser.
Weizsäcker made important theoretical discoveries regarding energy production in stars from nuclear fusion processes. He also did influential theoretical work on planetary formation in the early Solar System.
In his late career, he focused more on philosophical and ethical issues, and was awarded several international honors for his work in those areas.
Der bedrohte Friede. Politische Aufsätze 1945–1981, Hanser, München 1981, ISBN 3-446-13454-9.