Thomas Raynesford Lounsbury (January 1, 1838 – April 9, 1915)[1] was an American literary historian and critic.

He enlisted in the 126th New York Volunteers in 1862 and served in the Civil War as a first lieutenant.

It is as a student of Chaucer, of Shakespeare, and of the English language from the point of view of its development that he especially distinguished himself.

His editorial work includes: Chaucer's Parliament of Foules (1877); the Complete Works of Charles Dudley Warner (1904); and the Yale Book of American Verse (1912).

Professor Lounsbury wrote other important publications which include: Lounsbury was also the subject of some needling by Mark Twain, in his famous critique of James Fenimore Cooper ("Fenimore Cooper's Literary Offenses", written 1895).