The 2025 Port Macquarie state by-election was held on 15 March 2025 to elect the member for Port Macquarie in the New South Wales Legislative Assembly, following the resignation of Liberal Party MP Leslie Williams. Liberal candidate Robert Dwyer declared victory over Nationals candidate Sean Gleeson on 17 March 2025.
Port Macquarie was created in 1988 following a redistribution with the majority of the seat being inherited from Oxley. Throughout the history of the Mid North Coast region, like the rest of northern New South Wales, has been a stronghold of support for conservative parties. The seat was held by the National Party until 2002, when sitting member Rob Oakeshott left the party to become an independent. Oakeshott resigned in 2008 to successfully enter federal politics at the Lyne by-election, and was succeeded by independent Peter Besseling at the 2008 Port Macquarie state by-election.
Besseling lost his seat at the 2011 state election to Nationals candidate Leslie Williams. Williams was re-elected in 2015 and 2019, increasing her primary vote on both occasions.
On 20 September 2020, Williams left the Nationals to join the Liberal Party, citing the "reckless and unreasonable behaviour" of Nationals leader John Barilaro in threatening to end the Coalition and move the party to the crossbench due to a disagreement over koala protections. The Nationals contested Port Macquarie at the 2023 state election, but Williams retained the seat for the Liberals with a two-candidate-preferred vote of 60.8%.
On 22 January 2025, Williams announced that she would resign from parliament. She said she made the decision in order to be closer to her family in Western Australia after the death of her husband, Don Williams, in 2022. Her resignation officially came into effect on 31 January 2025.
Candidates are listed in the order they appeared on the ballot.
On 8 February 2025, Laurieton United Services Club and Kew Country Club general manager Robert Dwyer defeated real estate agent Luke Hadfield to win Liberal Party preselection.
On 9 February 2025, general practitioner Warwick Yonge was preselected by the Nationals as their candidate for the by-election. Three days later on 12 February 2025, the Nationals' Central Executive refused to endorse his candidacy without providing a public explanation. Nationals leader Dugald Saunders said Yonge had never been officially endorsed, and "further issues came to light" which made it "untenable from the perspective of Central Executive to actually endorse him as a candidate".
On 19 February 2025, beef cattle farmer Sean Gleeson was selected as the party's replacement candidate. Yonge announced on 27 February 2025 that he would contest the by-election as an independent.
Labor has traditionally polled poorly in Port Macquarie, only recording more that 40% of the two-party-preferred vote on one occasion (2003) since the seat was created in 1988, and the party chose not to contest the by-election.