Baron Karl von Hasenauer (German: Karl Freiherr von Hasenauer [ˈhaːzənaʊɐ]) (20 July 1833 – 4 January 1894) was an important Austrian architect and key representative of the Historismus school. He created several Neo-Baroque monuments, many around near the Ringstraße in Vienna. He was also a student of August Sicard von Sicardsburg and Eduard van der Nüll. For his outstanding work, he was ennobled by Emperor Franz Joseph I in 1873, and made Freiherr, the equivalent of baron.