Oswald Marian Balzer (1858–1933) was a Polishhistorian of law and statehood, one of the most renowned Polish historians of his times.
In 1887 he became a professor at the University of Lwów. Between 1895 and 1896 he also briefly served as its rector. Since 1891 until his death he was also the director of City Archives in Lwów. His best work is Genealogia Piastów (1895).In 1888 he was offered a seat in the Polish Academy of Skills, as well as several other scientific societies, both in Poland and abroad. In 1901 he founded the Society for the Support of Polish Science in Lwów (Tow. dla Popierania Nauki Pol. we Lwowie), the first such society in the city, later to be renamed to Lwow Scientific Society (1920). Among the fields of his studies were the history of Polish statehood and Poland's historical law, as well as the early history of Slavic states.