Labour was on target to win an outright majority of the seats in Parliament, something that hasn't happened since New Zealand implemented a proportional voting system 24 years ago. Typically, parties must form alliances to govern, but this time Ardern and Labour can go it alone.
In a victory speech in front of hundreds of cheering supporters in Auckland, Ardern said her party had gotten more support from New Zealanders that at any time in at least 50 years.
"This has not been an ordinary election, and it's not an ordinary time," she said. "It's been full of uncertainty and anxiety, and we set out to be an antidote to that."
Ardern promised not to take her new supporters for granted and to govern for all New Zealanders.
"We are living in an increasingly polarized world, a place where, more and more, people have lost the ability to see one another's point of view," she said. "I think in this election, New Zealanders have shown that this is not who we are."
A record number of voters cast early ballots in the two weeks leading up to the election.
On the campaign trail, Ardern was greeted like a rock star by people who crammed into malls and spilled onto streets to cheer her on and get selfies with her.