With 87% of the votes counted, Ardern's center-left Labour Party has won 48.9% of the vote, meaning her party looks likely to score the highest result that any party has achieved since the current political system was introduced in 1996.
"Tonight, New Zealand has shown the Labour Party its greatest support in at least 50 years," Ardern said in a powerful victory speech where she referred to the difficult times ahead for New Zealand. "And I can promise you: we will be a party that governs for every New Zealander."