The Honourable William John Wentworth-FitzWilliam (7 August 1852 – 11 September 1889), was a British Liberal politician.

Wentworth-FitzWilliam was the fifth son of William Wentworth-FitzWilliam, 6th Earl FitzWilliam, and his wife Lady Frances Harriet, daughter of George Douglas, 17th Earl of Morton. William Wentworth Fitzwilliam, Viscount Milton, was his elder brother and William Wentworth-FitzWilliam, 7th Earl FitzWilliam, his nephew. He entered Parliament for Peterborough in 1878, a seat he held until his death.

Wentworth-FitzWilliam died at Wentworth house in September 1889, aged 37, after he was thrown from his horse.