Gersau is first mentioned in 1064 as "Gersouwe". The estates of Gersau gradually came into the hands of the Habsburgs, but in 1333, under dukes Albert II and Otto IV "the Merry" of Austria, the jurisdiction and rights over Gersau fell into the hands of Lucerne nobility. On 1359, Gersau allied with the Old Swiss Confederacy as a protectorate of the Confederacy, for its protection and to gain arms from the confederates. On 9 July 1386, the citizens of Gersau fought with the Swiss for the first time, on the battlefield of Sempach, where the banner of Count Rudolf of Hohenzollern was captured.