Jacinda Ardern is officially the prime minister of New Zealand.
Governor-General Dame Patsy Reddy signed the warrant appointing Ardern as prime minister in a swearing in ceremony at Government House on Thursday morning.
The warrant officially appointing her deputy, NZ First leader Winston Peters, has also been signed.
More than 100 guests attended the ceremony where Ms Ardern described her new ministry as a strong and effective team.
"We have a responsibility now to all New Zealanders to do our very best to achieve the goals of this government, to be a government that is active, that is focused, that is empathetic and that is strong," she said.
"I look forward to working with all of you to make a positive difference for New Zealand."
Earlier National Party leader Bill English travelled to Government House with his wife Mary and youngest son Xavier to hand in his resignation.
He will continue to lead National and has committed to recontesting the 2020 election in that role.
Ardern gave her first major public speech in her new role yesterday.
Ardern arrived to rapturous applause and a standing ovation at the Council of Trade Unions conference in Wellington yesterday, and outlined a series of worker-friendly policies that will undo the work of the previous Government.
• restoring the right to meal and rest breaks and the duty to conclude bargaining
• restoring the right of union access to the workplace
• restoring the right of workers to initiate collective bargaining
The incoming Government will also lift the minimum wage to $20 an hour by April 2021, scrap the 90-day workers' trial, and introduce Fair Pay Agreements to set industry standards for pay and conditions.
Ardern said the unemployment rate should be below 4 per cent. It is currently 4.8 per cent - the lowest since 2008.
She also offered an olive branch to businesses, saying she would ask a tax working group to look at ways to help small businesses, such as a lower company tax rate for businesses with small turnover.
Earlier Ardern announced her Cabinet and executive. In addition to holding Arts, Culture and Heritage and National Security and Intelligence, Ardern will also have a new portfolio for Child Poverty Reduction.
"It's a personal priority for me, a commitment for me, one of the reasons I am in politics. It's my intention that I will establish a unit within [the Department of the Prime Minister and Cabinet] to undertake that work across government departments."
She confirmed that Grant Robertson will be Finance Minister, David Clark will be Health Minister, and Phil Twyford will be Transport Minister and Housing and Urban Development Minister.
Deputy leader Kelvin Davis will take a new portfolio of Crown/Maori Relations with a focus on the post-Treaty environment, as well as Corrections, Tourism and Associate Education.
Michael Wood was also named as a member of the executive yesterday, as under-secretary to the Minister for Ethnic Communities.
Ardern said having the Women's portfolio outside Cabinet with Green MP Julie Anne Genter did not diminish its importance.
"I am a woman," Ardern said. "I take the issue of things like equal pay, domestic violence, support for women in care-giving roles incredibly seriously."
Greens leader James Shaw will be Climate Change Minister and Statistics Minister. Deputy Prime Minister Winston Peters will pick up Foreign Affairs, as well as Racing and State Owned Enterprises.
Peters later said that there was a 38-page document about the Labour-New Zealand First coalition agreement - far lengthier than the seven-page document released on Tuesday.
"It's a document of precision on various areas of policy commitment and development."
He said it would be released in coming months, but when exactly would be up to Ardern.
In a video posted to Facebook last night, National leader Bill English thanked voters for their support and said it had been a privilege to be Prime Minister.
"Tomorrow morning [Thursday] at 9am I will leave the Beehive and go to Government House to hand in my resignation as Prime Minister."
- Additional reporting NZN