Thomas Cassells (7 August 1902 – 16 June 1944) was a Labour Party politician in Scotland who served as Member of Parliament (MP) for Dunbartonshire from 1936 to 1941.
He won the seat at a by-election in March 1936, when his predecessor resigned to become Governor of Burma.
A solicitor by training, Cassells held the seat until his appointment in 1941 as a Sheriff-substitute of Inverness, Elgin and Nairn, when he was succeeded at a by-election by Adam McKinlay.
Thomas Cassells was educated at Hamilton Academy where one of his teachers had been Robert Gibson, himself a former pupil of the school, and who was also to serve as a Labour MP (for Greenock) and over the same period, 1936–41.
This article about a Labour Party member of Parliament representing a Scottish constituency is a stub.