Frederick I of Prussia , ( 11 July 1657 -- 25 February 1713 ) of the Hohenzollern dynasty was the first King in Prussia ( 1701 -- 1713 ) . Frederick I ( 11 July 1657 â `` 25 February 1713 ) , of the Hohenzollern dynasty , was ( as Frederick III ) Elector of Brandenburg ( 1688 â `` 1713 ) and Duke of Prussia in personal union ( Brandenburg-Prussia ) . The latter function he upgraded to royalty , becoming the first King in Prussia ( 1701 â `` 1713 ) .