Wilhelm I, also known as Wilhelm "the Great" (1797 – 1888) of the House of Hohenzollern was the King of Prussia (January 2, 1861 – 9 March, 1888) and the first German Emperor (18 January 1871 – 9 March, 1888). Under the leadership of Wilhelm and his prime minister Otto von Bismarck, Prussia achieved the unification of Germany and the establishment of the German Empire.