| Election Name: | 1919 Plymouth Sutton by-election |
| Type: | presidential |
| Country: | United Kingdom |
| Previous Election: | Plymouth Sutton (UK Parliament constituency)#Elections in the 1910s |
| Previous Year: | 1918 |
| Next Election: | Plymouth Sutton (UK Parliament constituency)#Elections in the 1920s |
| Next Year: | 1922 |
| Election Date: | 28 November 1919 |
| Candidate1: | Nancy Astor |
| Party1: | Unionist Party (UK) |
| Popular Vote1: | 14,495 |
| Percentage1: | 51.9% |
| Candidate2: | W.T. Gay |
| Party2: | Labour Party (UK) |
| Popular Vote2: | 9,292 |
| Percentage2: | 33.3% |
| Candidate3: | Isaac Foot |
| Party3: | Liberal Party (UK) |
| Popular Vote3: | 4,139 |
| Percentage3: | 14.8% |
| Map Size: | 250px |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | Waldorf Astor |
| Before Party: | Unionist Party (UK) |
| After Election: | Nancy Astor |
| After Party: | Unionist Party (UK) |
The 1919 Plymouth Sutton by-election was a parliamentary by-election held on 28 November 1919[1] for the British House of Commons constituency of Sutton in the city of Plymouth, Devon.
The seat had become vacant when the constituency's Conservative Member of Parliament (MP), Waldorf Astor, succeeded the peerage as the second Viscount Astor on the death of his father on 18 October 1919.
Astor had held the seat since the 1918 general election, and its predecessor Plymouth since the December 1910 general election.
Lady Astor retained the seat. She became the first woman to take up her seat in the Commons (the first woman to be elected, Countess Markievicz, the Sinn Féin MP for Dublin St Patrick's, refused to take her seat).