| Election Name: | 1919 Liverpool West Derby |
| Type: | presidential |
| Country: | United Kingdom |
| Previous Election: | Liverpool West Derby (UK Parliament constituency)#Elections in the 1910s |
| Previous Year: | 1918 |
| Next Election: | Liverpool West Derby (UK Parliament constituency)#Elections in the 1920s |
| Next Year: | 1922 |
| Election Date: | 26 February 1919 |
| Candidate1: | Hall |
| Party1: | Unionist Party (UK) |
| Popular Vote1: | 6,062 |
| Percentage1: | 56.5 |
| Candidate2: | Nelson |
| Party2: | Labour Party (UK) |
| Popular Vote2: | 4,670 |
| Percentage2: | 43.5 |
| Map Size: | 250px |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | Smith |
| Before Party: | Unionist Party (UK) |
| After Election: | Hall |
| After Party: | Unionist Party (UK) |
The 1919 Liverpool West Derby by-election was a parliamentary by-election held on 26 February 1919 for the British House of Commons constituency of Liverpool West Derby, in the County Palatine of Lancashire.
The seat had become vacant on the elevation to the peerage of the constituency's Unionist Member of Parliament (MP), F. E. Smith, as Baron Birkenhead. He had been raised to the peerage to take up the post of Lord Chancellor.
Smith had held the seat since the 1918 general election, when he was endorsed by the Coalition Government. Before that he held its predecessor seat, Liverpool Walton since the 1906 general election.
Turnout was unsurprisingly low so soon after a General Election. Hall won the seat by a much reduced margin.