Heidenheim an der Brenz (German pronunciation: [ˈhaɪdn̩haɪm ʔan deːɐ̯ ˈbʁɛnts], lit. 'Heidenheim on the Brenz'), or just Heidenheim (German pronunciation: [ˈhaɪdn̩haɪm] ; Swabian: Hoidna or Hoirna), 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. Heidenheim is the economic center for all the communities in Heidenheim district and is the headquarters of the Voith industrial company. The town's population in 2021 was just below the 50,000 mark. Heidenheim collaborates with the town of Nattheim in administrative matters.
The residents of Heidenheim and its surrounding area speak the distinct German dialect of Swabian.