| Election Name: | 1921 Dover by-election |
| Type: | presidential |
| Country: | United Kingdom |
| Previous Election: | Dover (UK Parliament constituency)#Elections in the 1910s |
| Previous Year: | 1918 |
| Next Election: | Dover (UK Parliament constituency)#Elections in the 1920s |
| Next Year: | 1922 |
| Election Date: | 12 January 1921 |
| Candidate1: | Polson |
| Party1: | Independent politician |
| Popular Vote1: | 13,947 |
| Percentage1: | 56.3% |
| Candidate2: | Astor |
| Party2: | Unionist Party (UK) |
| Popular Vote2: | 10,817 |
| Percentage2: | 43.7% |
| Map Size: | 250px |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | Ponsonby |
| Before Party: | Unionist Party (UK) |
| After Election: | Astor |
| After Party: | Unionist Party (UK) |
The 1921 Dover by-election was held on 12 January 1921. The by-election was held due to the succession to the peerage of the incumbent Coalition Unionist MP, Vere Ponsonby as Ninth Earl of Bessborough. It was won by the Independent candidate Thomas Andrew Polson.
Polson's election was supported by Horatio Bottomley, but although claimed by Bottonmley as a member of the right-wing Independent Parliamentary Group, he joined the Anti-Waste League shortly after his election. Polson stood again at the general election in November 1922, but was defeated by the Unionist candidate John Jacob Astor, whom he had defeated at the by-election in 1921.[1]