The 1919 Swansea East by-election was a parliamentary by-election held for the British House of Commons constituency of Swansea East on 10 July 1919.
The seat had become vacant when the Coalition Liberal Member of Parliament (MP) Thomas Jeremiah Williams had died on 12 June 1919, aged 46. He had held the seat since its creation at the 1918 general election.
At a Labour Party conference in June, a resolution was passed in favour of using the strike weapon for political purposes.
The Coalition Liberal candidate, David Matthews, held the seat for his party, but with a greatly reduced majority.
David Williams stood again at the 1922 general election and won the seat for the Labour Party.