Ion I. Nistor (August 16, 1876 – November 11, 1962) was a prominent Romanian historian and politician. He was a member of the Romanian Academy after 1911, and served as administrator of its Library.
Nistor was born into a family of peasants in the Bivolărie hamlet of Vicovul de Sus, Bukovina — in Austria-Hungary at the time, it is now included in Suceava County, Romania. He studied at the local school in Vicovul de Sus, then at Elementary School of Rădăuţi and at the Rădăuţi German High School, getting his Matura in 1897.
He then studied Philosophy and Literature at the University of Czernowitz and between 1898 and 1900, he completed his military service in the Austro-Hungarian Army (serving in Polei and in Vienna), and graduated from the University in 1902, after which he was named teacher of history and geography at the Suceava Classic High school. Together with some of his friends, Nistor edited a magazine titled Junimea Literară between 1904 and 1914, first published in Rădăuţi and then in Suceava.
In 1904, Nistor married Virginia Pauliuc, daughter of the Gheorghe Pauliuc (a Romanian Orthodox priest from Burla), and, one year later, on July 5, 1905, Oltea, his only child, was born. He then moved to teach at the Orthodox High School, making use of the institution's library, better suited to his studies into the history of Moldavia.
In 1908-1909 and 1910–1911, he studied at the University of Vienna and completed his PhD under Konstantin Josef Jireček, with a thesis on Moldavia's aspirations regarding Pokuttya. After that, he furthered his studies at the Universities of Munich, Leipzig and Berlin, receiving (1911) his Docent title and the Venia legendi, which allowed him to teach at the University of Vienna, where he gave lectures on the history of the Romanians.