Albert Bushnell Hart (July 1, 1854 – July 16, 1943), was an American historian based at Harvard, writer, and editor. One of the first generation of professionally trained historians in the United States, a prolific author and editor of historical works, Albert Bushnell Hart became, as Samuel Eliot Morison described him, "The Grand Old Man" of American history, looking the part with his "patriarchal full beard and flowing moustaches."
Hart was born in Clarksville (now Clark), Mercer County, Pennsylvania. He graduated from Harvard University in 1880. He was a member of Phi Beta Kappa and a classmate and friend of future U.S. President Theodore Roosevelt. He studied at Paris, Berlin and Freiburg, and received his doctorate from Freiburg in 1883. Harvard President Charles Eliot appointed Hart an instructor in 1883 to teach the only course in American history that the college offered, despite the fact that Edward Channing, already an assistant in European history, wanted to teach the course himself. Hart served as instructor in history from 1883–87, assistant professor from 1887–97, and became a professor in 1897. In 1910 he was appointed Eaton Professor of the Science of Government. He was on the Harvard faculty for 43 years, retiring in 1926. In retirement he continued to write and edit from a room in Widener Library. He maintained a summer home in New Hampshire near Mount Monadnock.
Hart edited, along with Edward Channing, over the period from 1892 to 1895 a series of extracts from primary documents called the "American history leaflets; colonial and constitutional", which included titles such as "Extracts from the Sagas describing the voyages to Vinland", and "Documents illustrating the territorial development of the United States, 1584-1774". Hart was an editor of the Harvard Graduates' Magazine from 1894 to 1902. He served as president of the American Historical Association in 1909 and of the American Political Science Association in 1912. In 1914, he was appointed exchange professor at the University of Berlin.