Thomas Dummer (1739–1781) was an English Member of Parliament for Newport (Isle of Wight) (1765–1768), Yarmouth (Isle of Wight) (1769–1774), Downton in Wiltshire (1774), Wendover in Buckinghamshire (1775–1780) and Lymington in Hampshire (1780–1781).
Dummer was the son of Thomas Lee Dummer. On his father's death in October 1765, he succeeded him to the family estate at Cranbury Park near Winchester, Hampshire as well as estates at Weston and Netley, near Southampton and at Horninghold in Leicestershire. He also took his father's parliamentary seat at Newport. In 1768, he lost his seat to Hans Sloane who was in the patronage of the influential Hans Stanley.
In 1769, he became M.P. for nearby Yarmouth (1769–1774). Originally, the election was in favour of William Strode and Jervoise Clarke, but on petition the election was reversed in favour of Dummer and Major General the Hon. George Lane Parker.