| Country: | South Australia |
| Type: | parliamentary |
| Election Date: | 23 March 2024 |
| Seats For Election: | Electoral district of Dunstan in the South Australian House of Assembly |
| Previous Election: | 2022 South Australian state election |
| Previous Year: | 2022 |
| Next Election: | 2026 South Australian state election |
| Next Year: | 2026 |
| Turnout: | 24,447 (80.8% 8.9) |
| Candidate1: | Cressida O'Hanlon |
| Party1: | Australian Labor Party (South Australian Branch) |
| Popular Vote1: | 6,896 |
| Percentage1: | 32.1% |
| Swing1: | 3.1 |
| Candidate2: | Anna Finizio |
| Party2: | Liberal Party of Australia (South Australian Division) |
| Popular Vote2: | 9,334 |
| Percentage2: | 43.5% |
| Swing2: | 3.2 |
| Candidate3: | Katie McCusker |
| Party3: | Greens South Australia |
| Popular Vote3: | 4,116 |
| Percentage3: | 19.2% |
| Swing3: | 5.5 |
| 1Blank: | TPP |
| 2Blank: | TPP swing |
| 1Data1: | 50.8% |
| 2Data1: | 1.4 |
| 1Data2: | 49.2% |
| 2Data2: | 1.4 |
| MP | |
| Before Election: | Steven Marshall |
| Before Party: | Liberal Party of Australia (South Australian Division) |
| After Election: | Cressida O'Hanlon |
| After Party: | Australian Labor Party (South Australian Branch) |
A by-election for the seat of Dunstan in the South Australian House of Assembly was held on 23 March 2024, following the resignation of incumbent member and former premier Steven Marshall, which was announced on 24 January 2024.[1]
Labor candidate Cressida O'Hanlon was elected the new member, defeating Liberal candidate Anna Finizio. O'Hanlon is the first Labor member to represent the seat, and the only member other than Marshall to have represented the seat since its creation in 2014. It is the first instance of a governing party gaining a seat in a by-election from the Opposition in South Australia in over a century.
The by-election was triggered by the resignation of sitting Liberal MP and former premier Steven Marshall.
Dunstan is considered an ultra-marginal seat, sitting on a 0.5% margin. Indeed, at the 2022 state election, when Marshall's Liberal government unsuccessfully sought a second term (but were defeated in a landslide), Marshall came close to losing his own seat.
List of candidates as they appear on the ballot order.