The Bristol South East by-election, 1961 was a by-election held on 4 May 1961 for the British House of Commons constituency of Bristol South East in the city of Bristol.
The seat had become vacant when the constituency's Labour Member of Parliament (MP) Tony Benn had inherited from his father a hereditary peerage as Viscount Stansgate, thus making him ineligible to serve in the House of Commons. He had been elected at a by-election in 1950.
Benn stood in the by-election anyway, but due to his ineligibility, the Conservative Party candidate Malcolm St Clair was declared the winner.
When the law was later changed to allow Benn to renounce his peerage, St Clair resigned his seat, and Benn was returned to the House of Commons at the Bristol South East by-election, 1963.