Liza Harvey has been elected unopposed as leader of the Liberal party in Western Australia and Bill Marmion has been chosen as her deputy.
Liza Harvey says she is "pretty proud" to be elected the first woman to lead the Liberal party in Western Australia in a vote sparked by the sudden resignation of Mike Nahan.
Ms Harvey, a widow and mother, joined Mia Davies in the Nationals and Alison Xamon in the Greens as other females leading opposition parties.
"It's very significant ... I got here without being part of a quota - I'm pretty proud of that," she told reporters with a smile on Thursday.
Ms Harvey was deputy premier under Colin Barnett and has long been tipped as a leader.
Senior Labor minster Alannah MacTiernan tweeted her congratulations to Ms Harvey, saying it was a "great breakthrough for women in the Liberal party".
Ms Harvey said she was angry with how Labor was running the state and her focus would be holding the government accountable.
"There are 99,000 West Australians unemployed," she said.
"The government's increases in household fees and charges is not only impacting on families and their ability to keep their heads above water, it's impacting on small businesses.
"This government has got that GST windfall that we didn't receive when we were in government.
"I stand proud of the achievements of the Barnett government. We rebuilt the state."
Bill Marmion was chosen as the Liberals deputy leader over Tony Krsticevic, but the results of the ballot have not been revealed by the party.
Dr Nahan, the Michigan-born former state treasurer, took on the opposition leader role after the Barnett government suffered a thumping election loss in 2017.
But he was seen by some to be a "seat warmer" and was dogged by questions about his leadership over the past two years.
Dr Nahan took the unusual step of announcing his resignation via an interview with the ABC, saying he had set himself a goal to review his position halfway though the current four-year term.
"My goals were, after a loss like that, keep the team together, keep the government accountable, highlight as many flaws, and my decision was to review my position halfway through," he said on Wednesday night.
"I've decided to step down because I'm confident we are in a good position with a number of leadership aspirants and particularly after the federal election.
"People know after a loss like that the opposition leader is not the final one."
Dr Nahan said the airing of leadership discussions in the media prompted his resignation announcement.
Ms Harvey thanked Dr Nahan for his service and said he had been under a tremendous amount of pressure.
She noted the party had won two by-elections in WA and the federal election during his leadership.
"He will still be an integral part of our team, but I'd like to thank him for his leadership and for keeping our team together during those two very difficult years," she said.