Thomas Duncombe (baptised 27 August 1724 – 23 November 1779) was a British politician who sat in the House of Commons between 1751 and 1779. Duncombe was the eldest son of Thomas Duncombe, of Duncombe Park, North Yorkshire and his wife, Mary Slingsby, daughter of Sir Thomas Slingsby. He was educated at Westminster School from an early age in 1732, and matriculated at Christ Church, Oxford on 18 May 1742, aged 17. He succeeded his father to Duncombe Park in 1746 and is also known as Thomas Duncombe III.