William FitzWilliam, 5th Viscount FitzWilliam (1780-1857), was an English nobleman and politician. He was born into the FitzWilliam family, which held significant land and influence in Yorkshire. He served as a member of the House of Lords and was known for his contributions to local governance and public affairs. FitzWilliam inherited the title from his father and was involved in various charitable activities. He was also a prominent figure in the management of the family estate, Wentworth Woodhouse, which is one of the largest country houses in England. His legacy includes both his political work and his commitment to social causes.