The result was confirmed just after 2pm to Mauger and his team.
The current vote count shows the one-term councillor and former construction company owner has a narrow majority, with 50,086 votes.
His nearest rival, David Meates, received 46,315 votes.
The next highest-polling Mayoral candidate was Mark Chirnside who received 4164 votes.
Mauger said he was "relieved, humbled and excited" with the result.
He revealed what he did when he got the news.
"I punched the air, I thought 'this is fantastic," he said.
"The hard work starts now."
Mauger said he wanted to start that work this weekend.
"What I want to do tomorrow is get all the new councillors together to have a pow-wow," he said.
"How can we all work together and make sure we are pulling the rope in the same direction to make Christchurch the best place to live, work, invest and play in the whole country," he said
Mauger thanked Meates for his efforts in the campaign.
"Thank you for coming in and keeping me honest, for want of a better word," he said.
To have someone of David's calibre run shows the commitment we have in Christchurch to local democracy.
"It's always good to run with someone strong... It's always better to have a race and win well."
In a statement, Mauger said he was "very pleased that my message of regaining people's trust in Council and getting things done has resonated with so many people".
"I have consistently said during the campaign that I do not believe there is any place for party politics around the Council table.
"I promise to be a Mayor who listens to all ideas and works with people to get the best outcomes for our city.''
Mauger takes over from Lianne Dalziel who, after almost a decade in the mayoral chains, decided not to run again in this year's election.
In the role since 2013, Dalziel has steered Christchurch through the earthquake recovery, mosque attacks, fires, floods and the pandemic.
Mauger is married with five children and eight grandchildren.
He said he was committed to making sure Christchurch was the best city it could be.
"We must do this in the face of significant national and global challenges ahead of us," he said.
"We must address climate change and manage the impact of rising inflation. We cannot afford to balance these against each other – we must find ways to do both if we are going to better position Christchurch for the future.
"Thank you again to the people of Christchurch and Banks Peninsula for your trust in me.
"I am honoured to become our next Mayor and humbled by your support. I look forward to working with you, and for you, over the next three years – together we will get things done."
Meates spoke from a campaign function in the central city.
He said he was disappointed with the result but congratulated the winner on the "very, very close campaign".
"It's great to see the city has made a choice," he said.
"I wish Phil all the best for the future.
"Phil has got the best interests of the city at heart and it would be good to just make sure that the politics that have divided the city over the past few years are out of the equation and that Phil helps lead a council towards a vibrant, fonfident future making the best decisions for the city."
Before this year's election the mayor-elect led Mauger's Contracting, a third-generation company specialising in building subdivisions, roads, sewers, drains and water mains, which his family has been operating in Christchurch since 1970.
He stepped aside from that role to focus on his mayoral bid.
His election promises included improving ratepayer satisfaction and confidence in the council and the way it operates.
"We must lift our game and make sure our council is connected to our city," he said.
"The council needs to adopt a "can do" attitude focused on finding solutions to the hold-ups and getting the ball rolling. That attitude comes from practical leadership – which I can deliver.
"If I am elected Mayor, I will continue to spend time every fortnight, going around the traps to meet people and community groups across the city to listen to concerns.
"I am standing for mayor because I want to get stuff done. I will bring a practical approach to council and make the best decisions for our city."
The Canterbury Employers' Chamber of Commerce welcomed Mauger to the role this afternoon.
"Phil is an experienced businessman and has committed to improving economic outcomes, removing barriers to doing business, and unlocking the opportunities that Christchurch has to offer," said chief executive Leeann Watson.
"Phil is stepping into a role that is not without its' challenges and we look forward to working closely together to advance the interests of the business community throughout the next three years."
Mauger is one of a number of newly-elected leaders in the South Island.
In Invercargill former deputy Nobby Clark has been elected as mayor over NZME radio broadcaster Marcus Lush.
In Ashburton, Neil Brown remains in the top job.
Glyn Lewers has been elected mayor of the Queenstown-Lakes District, replacing Jim Boult who did not run this year.
-By Anna Leask
