BREISGAU, a district of Germany, in the grand duchy of Baden. It extends along the right bank of the Rhine from Basel to Kehl, and includes the principal peaks of the southern Black Forest and the Freiburg valley. The Breisgau, originally a pagus or gau of the Frankish empire, was ruled during the middle ages by hereditary counts. Of these the earliest recorded is Birtilo (962–995), ancestor of the counts and dukes of Zähringen. On the death of Berchthold V. of Zähringen in 1218, his coheiresses brought parts of the Breisgau to the counts of Urach and Kyburg, while part went to the margraves of Baden. At the close of the 13th century the Kyburg part of the Breisgau passed to the Habsburgs, who in 1368 acquired also the town and countship of Freiburg, which had been sold by the counts of Urach to the Freiburgers and given in pledge by them to the house of Austria in exchange for a loan of the purchase price, which they were unable to repay. The male Urach line becoming extinct in 1457, an heiress carried what remained of their possessions in the Breisgau to the house of Baden. In the struggle between France and Austria from the 17th century onwards the Breisgau frequently changed masters. In 1801 Austria was forced to cede it to Ercole III., duke of Modena, in compensation for the duchy of which Napoleon had deprived him. His successor Ferdinand took the title of duke of Modena-Breisgau, but on his death in 1805 the Breisgau was divided between Baden and Württemberg. The latter ceded its portion to Baden in 1810.
See Stokvis, Manuel d’histoire, &c. (Leiden, 1890–1893).