The 1878 Peterborough by-election was fought on 29 October 1878. The by-election was fought due to the death of the incumbent Liberal MP, George Hammond Whalley.
It was won and gained by the Independent Liberal candidate John Wentworth-FitzWilliam.[1]
| Party | Candidate | Votes | % | ±% | |
|---|---|---|---|---|---|
| Independent Liberal | John Wentworth-FitzWilliam | 1,360 | 50.5 | New | |
| Conservative | John Lawrance | 671 | 24.9 | +7.7 | |
| Liberal | James Hayes Raper | 653 | 24.3 | -43.9 | |
| Lib-Lab | George Potter | 8 | 0.3 | -14.3 | |
| Majority | 689 | 25.6 | N/A | ||
| Turnout | 2,692 | 80.6 | +6.5 | ||
| Independent Liberal gain from Liberal | Swing | ||||