Mr Littleproud announced on Tuesday he would resign as party leader, but would remain in parliament.
"I'm buggered and I've had enough," he told reporters in Canberra.
"I've got to a juncture where I believe it is time."
A meeting of Nationals members in parliament will be held by the end of the week to select a new leader.
In an emotional press conference alongside his wife Amelia, Mr Littleproud said he wanted to leave the leadership after the coalition was reformed in February.
"It'd be wrong for me to say that I'm the right person to continue to lead. That's tough for me to say. I think someone better can do it, because I don't have the energy.
"I'm done, but I'm proud of what I've done.
"I don't intend to retire from parliament. I love the people of Maranoa, and while it wouldn't be right to continue on as leader of the Nationals because I don't have the energy, it'd be wrong to also stay on because I don't have the energy to represent them properly as the leader of the National Party."
He first entered parliament in 2016 as the MP for Maranoa in Queensland, one of the safest seats in the country.
He was elected leader of the Nationals in 2022 after the coalition's election defeat.
Mr Littleproud attracted controversy after he announced he would not renew the coalition agreement with the Liberals over policy after the 2025 election, before reuniting.
A second split took place in January under his leadership following a dispute over hate speech laws, before the parties got back together.
Mr Littleproud said the time serving as Nationals leader since the coalition's record defeat in 2025 had been difficult.
"I'll serve my great party and this great coalition any way they want me to, but this is my time over as a leader," he said.
"I've done all I can do, and all I want to do is time for me to feel normal again. It's been a pretty rough road since the election."
The Nationals have been under pressure from One Nation, with Pauline Hanson's party rising in the polls.
Leadership rival Barnaby Joyce defected to One Nation at the end of 2025, but Mr Littleproud said he was not worried about the threat the party posed.
Mr Littleproud survived a leadership challenge from Queensland backbencher Colin Boyce in February.
Prime Minister Anthony Albanese said he wished Mr Littleproud well.
"It is a significant achievement to be chosen to lead your party and David can look back on his four years as leader of Nationals and ten years as member for Maranoa knowing he has given his utmost," he said in a statement.
Opposition Leader Angus Taylor paid tribute to the outgoing Nationals leader.
"He has played a crucial role ... in shaping the direction of the coalition, shaping the direction of policy across our side of politics over the last four years," he said.
"I have seen time and time again, he has stood up for his constituents.
"He stood up for people across rural and regional Australia."
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