Arthur Meier Schlesinger Jr., born Arthur Bancroft Schlesinger, was a Pulitzer Prize recipient and American historian and social critic whose work explored the liberalism of American political leaders including Franklin D. Roosevelt, John F. Kennedy, and Robert F. Kennedy. He served as special assistant and "court historian" to President Kennedy from 1961 to 1963. He wrote a detailed account of the Kennedy Administration, from the transition period to the president's state funeral, titled A Thousand Days. In 1968, he actively supported the presidential campaign of Senator Robert F. Kennedy until Kennedy's assassination in the Ambassador Hotel on June 5, 1968, and wrote the biography Robert Kennedy and His Times several years later.
He popularized the term "imperial presidency" during the Nixon administration by writing the book The Imperial Presidency.
His father was also a well-known historian.