Jan Oskar Kieniewicz (born 7 August 1938) is a Polish historian, diplomat and humanities professor. He specialised in the history of India (particularly pre-colonisation) and European, Spanish and Polish history. He is a member of the Collegium Invisibile and the jury for the KLIO Award.
Born in Warsaw to professor Stefan Kieniewicz, he graduated in history in 1960 and his doctorate in 1966, both from the University of Warsaw, where he also spent much of his academic career, serving as head of its Department of Spanish Studies (1975-1981) and deputy director of its Institute of History (1981-1988). He became a habilitated doctor in 1974 and was awarded the title of professor in the humanities in 1983, retiring as a full professor at the University of Warsaw.
He also served as Poland's ambassador to Spain (1990-1994) and as deputy director of the Instytutu Bada? Interdyscyplinarnych Artes Liberales (1996-2008). After retiring he remained a lecturer at the University of Warsaw's Faculty of Liberal Arts. He was awarded the Knight's Cross of the Order of Polonia Restituta in 2005 and the Officer's Cross of the same order in 2013.