The "Battle Cry of Freedom", also known as "Rally 'Round the Flag", is a song written in 1862 by American composer George Frederick Root (1820–1895) during the American Civil War. A patriotic song advocating the causes of Unionism and abolitionism, it became so popular that composer H. L. Schreiner and lyricist W. H. Barnes adapted it for the Confederacy.

George Frederick Root was a romantic American composer, who found particular fame during the American Civil War, with songs such as "Tramp! Tramp! Tramp!" and "The Battle Cry of Freedom". He is regarded as the first American to compose a secular cantata.