| Country: | Victoria |
| Type: | parliamentary |
| Ongoing: | no |
| Election Date: | 2 March 1940 |
| Vote Type: | Popular |
| Image1: | John Dedman.jpg |
| Candidate1: | John Dedman |
| Party1: | Australian Labor Party |
| Popular Vote1: | 26,122 |
| Percentage1: | 51.8% |
| Swing1: | 8.3pp |
| Candidate2: | James Vinton Smith |
| Party2: | United Australia Party |
| Popular Vote2: | 22,878 |
| Percentage2: | 45.3% |
| Swing2: | 11.2pp |
| MP | |
| Before Election: | Richard Casey |
| Before Party: | United Australia Party |
| After Election: | John Dedman |
| After Party: | Australian Labor Party |
| Election Name: | 1940 Corio by-election |
| 1Data2: | 45.6% |
| 2Blank: | TPP swing |
| 2Data1: | 10.9pp |
| 2Data2: | 10.9pp |
| 1Data1: | 54.4% |
| 1Blank: | TPP |
A by-election was held for the Australian House of Representatives seat of Corio on 2 March 1940. This was triggered by the resignation of United Australia Party MP Richard Casey to become Australian Ambassador to the United States.
The by-election was won by Labor candidate John Dedman.