A left-wing progressive standard-bearer has won Toronto's mayoral election, triumphing in a historically crowded field of 102 candidates.

Olivia Chow, 66, said she will work to build a city that is "more caring, affordable and safe".

The race had focused largely on affordability and public safety.

It is the second time in eight months Torontonians voted for a mayor following the sudden resignation of incumbent John Tory.

The Hong Kong-born Ms Chow is a well-known veteran of Canadian progressive politics.

In her victory speech, she spoke of her immigrant roots, recalling coming to Canada at age 13.

Canada's most populous city is a place "where an immigrant kid can be standing in front of you as your new mayor".

"Toronto is a place of hope, a place of second chances," she said.

"While I've been knocked down, I always got back up," Ms Chow said. "Because the people of this city are worth the fight."

The mayoral byelection was launched after former mayor Mr Tory, 68, a moderate conservative, stepped down in February, hours after the Toronto Star newspaper reported he had an affair with a 31-year-old staffer during the Covid-19 pandemic.

Just months earlier, Mr Tory had cruised into a third term, securing over 60% of the vote.

This was Toronto's first mayoral race without an incumbent since 2014 and no clear centre-right successor to Mr Tory emerged.

Support failed to coalesce around those challengers - including former police chief Mark Saunders, who received some support from Ontario Premier Doug Ford, and former deputy mayor Ana Bailão, who received a last-minute endorsement from Mr Tory - giving Ms Chow a narrow path to victory.

She received about 37% of the vote in Monday's race.

With Ms Chow's win, it will be the first time in a decade that a progressive will lead the city, and her victory suggests potential future clashes with Mr Ford, the conservative premier who said earlier this month that she would be "an unmitigated disaster".

But on Monday Mr Ford congratulated Ms Chow on Twitter, saying "she has proven her desire and dedication to serving the city".

"I will work with anyone ready to work with our government to better our city and province," he said.

Once sworn in, Ms Chow will assume the new "strong mayor" powers granted last year by Mr Ford's provincial government.

These powers include hiring and firing power over senior city staff and - in certain instances - powers to pass bylaws with just one-third support of council.

She has said she will not use the new powers handed to a number of municipalities in the province.

Ms Chow served as a city councillor for downtown Toronto before being elected to federal parliament in 2006. She was married to the late federal NDP leader Jack Layton, who died in 2011.

She previously ran for mayor in 2014 but came in third.

Her campaign in this race focused on Toronto's housing affordability crisis, with promises to build homes on city-owned land and provide more support for renters.

Her platform included more help for the city's homeless population, such as adding more social housing and the creation of "respite spaces" - where Torontonians could access showers and meals, and other critical services - that would be open around the clock.

But she faced criticism for failing to reveal how much she would raise property taxes to pay for her promises.

The date for her swearing in has yet to be determined.