Thomas Hamilton, 9th Earl of Haddington (21 June 1780 - 1 December 1858) was a British Conservative politician and statesman. He served as an MP from 1802 to 1827, when he was raised to the peerage as Baron Melros of Tyninghame, and inherited his grandfather's Scottish earldom in 1828. He later served as Lord Lieutenant of Ireland and First Lord of the Admiralty in the governments of Sir Robert Peel.

|- style="text-align: center;" | width="30%" |Preceded by:
The Earl of Minto | width="40%" style="text-align: center;" |First Lord of the Admiralty
1841–1846 | width="30%" |Succeeded by:
The Earl of Ellenborough

|- style="text-align: center;" | width="30%" |Preceded by:
The Duke of Buccleuch and Queensberry | width="40%" style="text-align: center;" |Lord Privy Seal
1846 | width="30%" |Succeeded by:
The Earl of Minto