David Littleproud will lead the federal Nationals in opposition after a partyroom vote in Canberra.
Senator Perin Davey has been elected as deputy leader of the Nationals.
Mr Littleproud defeated incumbent leader Barnaby Joyce and former minister Darren Chester in a three-way contest to lead the party.
The leadership was determined at the first meeting of Nationals senators and MPs since the Coalition's election loss.
Mr Littleproud said it had been his dream to lead the party since he joined it as a six-year-old boy, 40 years ago.
"I believe passionately in the National Party … we are the conscience of rural and regional Australia right here in this parliament," he said.
"The National Party today starts its journey towards 2025, with a vibrant team, ready to articulate the policies that are important to regional and rural Australia, but also to draw on the experience of two former deputy prime ministers in Barnaby Joyce and Michael McCormack, to build that bridge of unity and purpose, to make sure that regional and rural Australia isn't forgotten."
Deputy leader Senator Davey said the Nationals would act in the interest of regional Australia from opposition.
"We've got three years to make sure we hold the new government to account, and to make sure they don't forget the regions, and they don't sell us short by doing deals with other parties and other interests," she said.
"So, my focus with David is eyes on the future, and we will continue to build and continue to be a very strong voice for the regions."
In a statement, Mr Joyce congratulated the new leadership team, saying they had "a mighty task ahead of them".
"I suppose you think I am sad. Not really," he said.
"Now, I have a chance to get back to my second greatest love, after my family, and that is my beloved people of New England, where I will have more time to get around my electorate and to be a person of service to them."
Nationals won't abandon 'net zero' climate commitment
The Coalition saw swings against it in urban centres and across regional Australia, amid perceptions that the Nationals were reluctant to embrace action on climate change.
Former leader Mr Joyce was previously a vocal opponent of a 2050 goal for net-zero emissions, but led the Nationals into a net-zero agreement with the Liberal Party.
Mr Littleproud said the leadership vote was not about "lurching" left or right, but finding the "sensible centre", and he would uphold the net-zero commitment.
"We have made a sensible decision to be part of the global community; the global community asked us to sign up to net zero by 2050," he said.
The Nationals party room spills the leadership positions after every election.
It kept all 16 of its lower house seats at the election, but the majority of its MPs suffered swings against them.
