Reinhart Koselleck (23 April 1923, Görlitz - 3 February 2006, Bad Oeynhausen) was a German historian, considered as one of the most important historians of the twentieth century. He held an original position in the historical discipline and was not part of any historical 'school', working in such varied fields as the epistemology of history, the history of concepts, linguistics, the foundations of an anthropology of history and social history, the history of law and the history of government.
His works notably dealt with Prussia and Germany in the 18th and 19th centuries. He was best known for his doctoral thesis Critique and Crisis (1954), strongly influenced by the thought of Carl Schmitt, his work in theGeschichtliche Grundbegriffe (1972-1997), and his work Futures Past (1979).