The House of Frohburg (also Froburg) was a noble family in medieval Switzerland, with possessions in what is now the canton of Solothurn. They originate in the Wigger basin, near Zofingen. In the 10th century, they built Frohburg Castle on a hill near Trimbach.They had the title of counts from the later 11th century. They ruled the lands between Olten and Solothurn, and took parts of Aargau and Sisgau as fief from the bishop of Basel.They reached the peak of their power in the later 12th and early 13th century, building a number of castles, and founding towns such as Aarburg, Liestal, Olten (then a fortified river crossing), Waldenburg, Wiedlisbach and Zofingen. They also founded Schöntal Abbey near Waldenburg.The House of Frohburg was divided into three branches, Neu-Homberg, Waldenburg a