The 1931 Sunderland by-election was held on 26 March 1931. The by-election was held due to the death of the incumbent Labour MP, Alfred Smith. Smith and his Labour colleague Dr Marion Phillips had gained the two-member seat at the last general election from the Conservatives Luke Thompson and Walter Raine, who had first won it in 1922[1] Another defeated candidate in 1929 was the Liberal Dr Betty Morgan, then aged 24.[1] Both Thompson and Morgan contested the by-election.
The by-election saw Luke Thompson narrowly regain the seat he had lost in 1929 for the Conservatives. At the general election held later in the year, Thompson was returned with a greatly increased majority of over 23,000 votes, and his fellow Conservative Samuel Storey was also comfortably elected as the seat's second member.[2]