Francis Lieber (March 18, 1798, Berlin, Germany - October 2, 1872, New York City), originally known as Franz Lieber, was a German-American jurist and political philosopher. He is most widely known as the author of the Lieber Code during the American Civil War, also known as Code for the Government of Armies in the Field (1863), which laid the foundation for conventions governing the conduct of troops during wartime.

While still in Germany, Lieber fought in the Prussian army during the Napoleonic wars, and was wounded during the Battle of Waterloo. Upon return to Germany after the war, he was persecuted by the authorities and not permitted to attend any university in Prussia. Disillusioned, he obtained a degree at Jena and later fled to England. He moved to Boston in 1827, where he became a founder and editor of Encyclopedia Americana. A decade later he became a professor of history and political economics at South Carolina College (now Univ. of South Carolina), where he remained until 1856. From 1856 until his death he taught at Columbia University.

Besides the Lieber Code, he published three philosophical books of note: A Manual of Political Ethics (1838), Essays on Property and Labor (1841), and On Civil Liberty and Self-Government (1853).