Justin Stevens said it had been an "incredibly tough but immensely rewarding" tenure in the role, as he announced his immediate departure on Wednesday.
"For reasons both professional and personal, now is the right time for me to move on and for someone else to take over the helm of the best news team in the country," he said on his LinkedIn page
Mr Stevens, who worked at the broadcaster for 19 years, said the ABC was the nation's most complex and scrutinised news organisation.
"I have sought to strengthen and defend our journalism without being blind to our stumbles," he said.
"It has been a huge four years, (and) our investigations have had major impacts for the public good."
ABC managing director, Hugh Marks, said Mr Stevens has been incredibly committed to the broadcaster and achieved outstanding results while new director.
"I am grateful to have seen the strength of Justin's editorial instincts and to have observed his commitment to the ABC and audiences," he said.
"I wish him every success in the future."
Mr Stevens said ABC News Loop and News Verify, the federal election coverage, and bolstered Indigenous affairs and climate reporting were among the broadcaster's achievements while he was in the news director role.
"The work of our teams is resonating with the public (and) we are number one in digital," he said.
"Our 7pm audience has grown, (and) the news channel is stronger than ever.
"We remain the most trusted news organisation in the country."
Mr Stevens' resignation follows industrial action at the ABC earlier in the year amid pay negotiations with staff.
There were also several controversies within the ABC during Mr Stevens' time as news director, including the 2022 Line of Fire reports. He apologised on behalf of the broadcaster for the inaccurate use of gunshots and the potentially misleading use of a quote as part of the Four Corners program.
He was also in charge when high-profile presenter Stan Grant resigned after criticism for his comments on colonialism during King Charles' coronation.
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