Thomas Willoughby, 4th Baron Middleton (19 December 1728 – 2 November 1781), was a British politician who sat in the House of Commons from 1762 to 1774, when he succeeded to the peerage as Baron Middleton.
He married Georgina, daughter of Evelyn Chadwick of West Leake, Nottinghamshire, in 1770 and lived in the family seat at Wollaton Park, Nottinghamshire. They had no children and was succeeded in the barony and estates by his cousin, Henry Willoughby, 5th Baron Middleton.
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- "WILLOUGHBY, Hon. Thomas (1728–81), of West Leake, Notts". History of Parliament Online. Retrieved 1 November 2017.
- "Willoughby pedigree 3". Retrieved 3 January 2006.