Thomas Thynne, 1st Marquess of Bath, 3rd Viscount Weymouth (1734-1796), English politician, was the elder son of Thomas Thynne, 2nd Viscount Weymouth (1710—1751), and the great-grandnephew of Thomas Thynne (c. 1640—17I4 ), who was created Baron Thynne and Viscount Weymouth in 1682. His mother was Louisa (d. 1736), daughter of John Carteret, 1st Earl Granville, and a descendant, of the family of Granville who held the earldom of Bath from 1661 to 1711. The Thynnes are descended from Sir John Thynne, the builder of Longleat, the splendid seat of the family in Wiltshire. Sir John owed his wealth and position to the favour of his master, the protector Somerset; he was comptroller of the household of the Lady Elizabeth, and was a person of some importance after that princess became queen. Another famous member of this family was Thomas Thynne (1648—1682), called on account of his wealth "Tom of Tea Thousand." He is celebrated by Dryden as Issachar in Absalom and Achitophel, and was murdered in London by some Swedes in February 1682.

Born on 13 September 1734 Thomas Thynne succeeded his father as 3rd Viscount Weymouth in January 1751 and was Lord Lieutenant of Ireland for a short time during 1765, although he never visited that country. Having, however, become prominent in English politics he was appointed Secretary of State for the Northern Department in January 1768; he acted with great promptitude during the unrest caused by John Wilkes and the Middlesex election of 1768. He was then attacked and libelled by Wiikes, who was consequently expelled from the House of Commons. Before the close of 1768 he was transferred from the northern to the southern department, but he resigned in December 1770 in the midst of the dispute with Spain over the possession of the Falkland Islands. In November Weymouth returned to his former office of secretary for the southern department, undertaking in addition the duties attached to the northern department for a few months in 1770, but he resigned both positions in the autumn of this year. In 1789 he was created Marquess of Bath, and he died in November 1796. Weymouth was a man of considerable ability, especially as a speaker, but according to more, modern standards, his habits were very coarse, resembling those of his friend and frequent companion, Charles James Fox. Horace Walpole refers frequently to his idleness and his drunkenness, and in early life at least "his great fortune he had damaged: by such profuse play, that his house was often full of bailiffs." He married Elizabeth (d. 1825), daughter of William Bentinck, 2nd Duke of Portland, by whom he had three sons and ten daughters.

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Henry Seymour Conway | width="40%" style="text-align: center;" |Northern Secretary
1768 | width="30%" |Succeeded by:
The Earl of Rochford

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The Earl of Rochford

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The Earl of Hillsborough

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The Earl of Suffolk | width="40%" style="text-align: center;" |Northern Secretary
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The Viscount Stormont