| Election Name: | 1903 Dulwich by-election |
| Type: | presidential |
| Country: | United Kingdom |
| Previous Election: | Dulwich (UK Parliament constituency)#Elections in the 1900s |
| Previous Year: | 1900 |
| Next Election: | Dulwich (UK Parliament constituency)#Elections in the 1900s |
| Next Year: | 1906 |
| Election Date: | 15 December 1903 |
| Candidate1: | Harris |
| Party1: | Conservative Party (UK) |
| Popular Vote1: | 5,819 |
| Percentage1: | 57.0% |
| Candidate2: | Masterman |
| Party2: | Liberal Party (UK) |
| Popular Vote2: | 4,382 |
| Percentage2: | 43.0% |
| Map Size: | 250px |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | Maple |
| Before Party: | Conservative Party (UK) |
| After Election: | Harris |
| After Party: | Conservative Party (UK) |
The 1903 Dulwich by-election was a by-election held on 15 December 1903 for the British House of Commons constituency of Dulwich in South London.
The by-election was triggered by the death of the serving Conservative Party Member of Parliament (MP), Sir John Blundell Maple.
The main issue in the by-election, as with the Lewisham by-election held on the same day, was tariff reform. Harris was a supporter of Joseph Chamberlain's proposals for Imperial Preference and was supported by the Tariff Reform League. Masterman was a supporter of the Liberal party policy of Free trade. Harris's involvement in the Jameson Raid affair was raised by his opponents.