Heidenheim an der Brenz, or just Heidenheim, is a town in Baden-Württemberg in southern Germany. It is located near the border with Bavaria, approximately 17 km south of Aalen and 33 km north of Ulm. Heidenheim is the largest town and the seat of the district of Heidenheim, and ranks third behind Aalen and Schwäbisch Gmünd in size among the towns in the region of East Württemberg.