| Election Name: | 1909 Croydon by-election |
| Type: | presidential |
| Country: | United Kingdom |
| Previous Election: | Croydon (UK Parliament constituency)#Elections in the 1900s |
| Previous Year: | 1906 |
| Next Election: | Croydon (UK Parliament constituency)#Elections in the 1910s |
| Next Year: | Jan. 1910 |
| Election Date: | 29 March 1909 |
| Candidate1: | Hermon-Hodge |
| Party1: | Conservative Party (UK) |
| Last Election1: | 8,211 |
| Popular Vote1: | 11,989 |
| Percentage1: | 57.4% |
| Candidate2: | Raphael |
| Party2: | Liberal Party (UK) |
| Last Election2: | 7,573 |
| Popular Vote2: | 8,041 |
| Percentage2: | 38.4% |
| Candidate3: | Smith |
| Party3: | Labour Party (UK) |
| Last Election3: | 4,007 |
| Popular Vote3: | 886 |
| Percentage3: | 4.2% |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | H. O. Arnold-Forster |
| Before Party: | Liberal Unionist Party |
| After Election: | Robert Hermon-Hodge |
| After Party: | Conservative Party (UK) |
The 1909 Croydon by-election was held on 29 March 1909. The by-election was held due to the death of the incumbent Liberal Unionist MP, H. O. Arnold-Forster. It was won by the Conservative candidate Robert Hermon-Hodge.