Arthur Meier Schlesinger Sr. was an American historian who taught at Harvard University, pioneering social history and urban history. He was a Progressive Era intellectual who stressed material causes and downplayed ideology and values as motivations for historical actors. He was highly influential as a director of PhD dissertations at Harvard for three decades, especially in the fields of social, women's, and immigration history. His son, Arthur M. Schlesinger Jr. (1917–2007), also taught at Harvard and was a noted historian.