Joanna of Pfirt

Joanna of Pfirt (c. 1300–1351) was heiress of Count Ulrich III of Pfirt. When her father died in 1324, she inherited his Sundgau lands. By the treaty of Thann she ceded her lands to the Habsburgs, giving them a contiguous territory in southern Alsace, and married Albert II of Austria.

She became Duchess of Austria in 1330, the year polyarthritis began to cripple her husband. Travel pained him, so he sent her on diplomatic missions; in 1336 she mediated peace between the Habsburgs and the House of Luxembourg over the Carinthian inheritance.

After years without a child, she bore Rudolf IV in 1339, aged thirty-nine. Six of her children survived, among them Leopold III, whose birth in 1351 cost her her life.