Oskar Halecki (26 May 1891, Vienna - 17 September 1973 White Plains, New York) was a Polish historian, social and Catholic activist.
As a historian, Halecki was an expert on medieval history of Poland and Lithuania, and history of Byzantine Empire.
Halecki was one of the founders of Polish Institute of Arts and Sciences of America in 1942, its first Executive Director and later its President (1952–1964). He was an expert of the Polish delegation at the Paris Peace Conference (1918–1919); member of League of Nations Secretariate (1921–1924); member of Warsaw Scientific Society since 1927; chairman of Polish Heraldic Society (1930–1939); member of the Polish Academy of Arts and Sciences in Kraków (1944–1961).
After graduating from the Jagiellonian University (1909–1914), he continued his education at the University of Vienna (1914–1915) and from 1915 became a docent at the Jagiellonian. Halecki moved to the Warsaw University in 1918 where he became a president of the Chair of History of Eastern Europe and became a professor in 1919, a dean of the Faculty of Philosophy (1920) and a dean of the Faculty of Humanities (1930–1931). Member of Polish Academy of Learning; professor of Fordham University (1944–1961), and Columbia University; visiting professor in Rome, Montreal and Berkeley.
Halecki also served on the controversial "Committee of Ten" in Scarsdale, New York, which claimed Communist influence in the public school curriculum during the 1950s.[1]
Doctor honoris causa of the University of Lyon, University of Montreal, De Paul University and Fordham University.