William Widdrington, 4th Baron Widdrington (1678 – 19 April 1743), was an English Roman Catholic peer and supporter of the Stuart claim to the Crown.
Widdrington was the son of William Widdrington, 3rd Baron Widdrington, by the Honourable Alethea Fairfax, daughter of Charles Fairfax, 5th Viscount Fairfax of Emley, and succeeded to his father's title and estates in 1695. He was a member of a staunchly Roman Catholic family and was educated at a Jesuit college in Paris. He became a supporter of the Stuart claim to the Crowns of England, Scotland, and Ireland.
Widdrington took part in the Jacobite rising of 1715, and with two of his brothers was taken prisoner after the Battle of Preston. He was convicted of high treason and condemned to death, but was reprieved after an intervention by Catherine Graham. Although his title and estates were forfeited, he was not executed but was allowed to retire to Bath.
Widdrington married Jane Tempest in 1700 and resided at Stella Hall, Blaydon-on-Tyne, Northumberland. His wife Jane died in 1714, and in 1718 he married Catherine Graham. In 1739, Catherine and her sister Mary inherited the estate at Nunnington Hall, Yorkshire, from their nephew Charles, third and last Viscount Preston, who died without issue. After his death on 17 April 1743, he was interred in his wife's family vault at Nunnington Parish Church. When his son Henry Francis Widdrington, who claimed the barony, died in September 1774, this branch of the family appears to have become extinct.
His brother Peregrine and sister-in-law Maria, Duchess of Norfolk, were both staunch Jacobites as well.