The 1956 Tonbridge by-election was held on 7 June 1956 due to the resignation of the Conservative Member of Parliament, Gerald Williams. It was retained by the Conservative candidate Richard Hornby. Although Tonbridge was usually a safe Conservative seat, this election was fought with a local Labour politician and against the backdrop of Anthony Eden's unpopular government, so the Conservative majority was cut to barely 1,600 votes.
| Party | Candidate | Votes | % | ±% | |
|---|---|---|---|---|---|
| Conservative | Richard Hornby | 20,515 | 52.0 | −8.4 | |
| Labour | Robert L Fagg | 18,913 | 48.0 | +8.4 | |
| Majority | 1,602 | 4.0 | −16.8 | ||
| Turnout | 39,428 | ||||
| Conservative hold | Swing | ||||