William I, also known as Wilhelm I (full name: William Frederick Louis, German: Wilhelm Friedrich Ludwig, March 22, 1797 –  March 9, 1888), of the House of Hohenzollern, is the King of Prussia (January 2, 1861 – March 9, 1888) and the first German Emperor (January 18, 1871 – March 9, 1888).

Under the leadership of William and his Chancellor Otto von Bismarck, Prussia achieve the unification of Germany and the establishment of the German Empire.