Jakob Emanuel Lange (2 April 1864 – 27 December 1941), was a Danish mycologist who studied the systematics of gilled mushrooms.
His best-known work is Flora Agaricina Danica, a five-volume plate work on the Agaricales of Denmark.
He was also a dedicated Georgist land reformer.He was the father of Morten Lange (1919–2003), mycologist, professor at the University of Copenhagen and member of the Folketing.