Pauline Hanson's One Nation has won its first seat in the Australian House of Representatives, three decades after she founded the party. David Farley, a 69-year-old agribusiness consultant, took the southern New South Wales seat of Farrer in Saturday's by-election, ending a 77-year run of Coalition members holding the electorate.

Farley secured 39.4 per cent of the primary vote, ahead of Climate-200-backed independent Michelle Milthorpe on 28.4 per cent. With more than 80 per cent of ballots counted by Saturday night, Farley was on roughly 57 per cent of the two-candidate-preferred vote — a comfortable margin in a seat the Liberals had treated as ancestral.

The vacancy was triggered by Sussan Ley's resignation in February after losing the Liberal leadership ballot to Angus Taylor. The Australian Labor Party opted not to field a candidate, leaving the contest as a fight between the Coalition, One Nation and an independent — a configuration the Liberal organisation has acknowledged disadvantaged it from the start.

Hanson, addressing supporters in Albury, said the result vindicated a 30-year project. "We're coming after those other seats," she said, naming a string of regional electorates held by Liberal and National incumbents. The party is already preparing candidates for the Victorian state election later this year.

Farley campaigned on water reform under the Murray-Darling Basin Plan, regional cost-of-living pressures and what he called the "complacency" of the major parties on rural issues. The seat's farming towns — Griffith, Leeton, Narrandera — recorded some of the largest swings against the Coalition.

For the Liberals, the result lands at an awkward moment. Taylor's leadership was already under quiet pressure following the February ballot, and senior Coalition figures spent Saturday night fielding questions about preference deals with One Nation in seats where the two parties now compete directly.

Antony Green, the ABC's longstanding election analyst, called the result a structural shift rather than a one-off protest vote, citing One Nation's primary support across both rural towns and irrigation belts. He noted that the Coalition has lost a regional safe seat to a non-major party only a handful of times in modern federal history.

Prime Minister Anthony Albanese, asked about the outcome on Sunday morning, said voters were "sending a message to the Coalition" rather than to his own government. Labor's decision to sit out the contest will draw scrutiny in coming weeks as Farley takes his seat in Canberra.