Hohenstaufen was a dynasty of Kings of Germany, many of whom were also crowned Holy Roman Emperor. The proper name, taken from their castle in Swabia, is Staufen.
When the last member of the Salian dynasty, Henry IV, Holy Roman Emperor, died without an heir there was controversy about the succession. Frederick and Conrad, the two current male Staufens, were grandsons of Henry III, Holy Roman Emperor and nephews of Henry IV. After the death of the intervening king and emperor Lothar II of Supplinburg, in 1137, Conrad became Conrad III of Germany.