Mr. Trudeau will remain in both roles until he is replaced as the head of the Liberal Party, a process that could take several months. His successor would then become prime minister, at least until federal elections are held.
The abrupt and acrimonious resignation of an influential Trudeau deputy last month highlighted his deep unpopularity after nearly a decade in power.
Here’s what to know about Mr. Trudeau’s rise and fall, and what could happen next.
What will happen to Canada’s government?
Mr. Trudeau shut down Parliament until late March — a process known as prorogation — creating a lengthy pause to allow the Liberal Party’s members to choose their next leader.
After a new party leader is chosen, the next step would be to head to a federal election. Canada’s next election must be held by October, but a vote could be called or forced earlier.
The Liberal government under a new prime minister could be short lived. Shortly after the new session begins, the Liberal government is likely to face a vote of confidence. It would likely lose such a vote, as it only commands a minority of the seats in Parliament and it has lost the support of all other parties. That would prompt a federal election.
The prime minister also has the power to dissolve Parliament at any time, which would also prompt an election.
What does it mean to prorogue Parliament?
Prorogation ends the current session of Parliament without dissolving it, which essentially halts all parliamentary business. The Governor General, the official head of state as King Charles’ representative, takes the action to prorogue Parliament, at the request of the Prime Minister.
Once Parliament is prorogued, all current bills and motions are removed from the agenda, and all committees stop meeting.
While Parliament is prorogued, the activities of the legislative branch are paused, but the rest of the government continues to function.
Who is Justin Trudeau?
Mr. Trudeau grew up in the spotlight as the son of Pierre Elliott Trudeau, a Canadian prime minister. In 2015, at age 43, Mr. Trudeau became Canada’s second-youngest leader after his Liberal Party won a strong parliamentary majority. Mr. Trudeau was savvy with social media and enjoyed a long political honeymoon after his election. (He also had good hair.)
In 2017, Mr. Trudeau came under pressure to stand up to Donald J. Trump, the newly elected U.S. president. As Mr. Trump restricted immigration, Mr. Trudeau restated Canada’s openness to asylum seekers, proclaiming, “Diversity is our strength.”
During his time in office, Mr. Trudeau prioritized two issues. One was climate change. The other was reconciliation with Indigenous people, over the generational harms from a system of boarding schools that were rife with abuse. He also followed through on a pledge to legalize marijuana.
In 2019, the Liberals maintained their hold on power with Mr. Trudeau as their leader, but by a narrower margin, and they failed to secure a majority in Parliament. The Liberals needed support from smaller parties to advance Mr. Trudeau’s legislative agenda.
During the coronavirus pandemic in 2020, Mr. Trudeau became the first Group of 7 leader to isolate himself, after his wife, Sophie Grégoire Trudeau, tested positive for Covid-19. (The couple are now separated.) The next year, when his approval ratings were still relatively high, he called a snap election, saying he wanted a strong mandate for his party to lead Canada out of the pandemic and into economic recovery.
Voters returned him to office in 2021, but the Liberals failed again to win a majority of votes in Parliament. Mr. Trudeau has since faced intense criticism from the Conservative opposition for some of his pandemic and recovery policies.
Why is his government unpopular?
Economy: Canada’s post-pandemic inflation spiked to 8 percent, though it has since receded below 2 percent. Unemployment remains high, around 6.4 percent. The Conservative opposition has hammered Mr. Trudeau’s carbon-tax program.
Housing: The cost of housing in many major Canadian cities has become untenable. An economic analysis this year found that in Toronto, Vancouver and Montreal, prices would have to plummet, or incomes would have to improbably soar, to restore affordability.
Immigration: In October, Mr. Trudeau said he was tightening Canada’s immigration policies after the country welcomed nearly three million people over three years, straining health care and other services. “In the tumultuous times as we emerged from the pandemic, between addressing labor needs and maintaining population growth, we didn’t get the balance quite right,” he said.
Scandals: In 2018, Mr. Trudeau was accused of groping a reporter in 2000, an allegation he rejected. A federal ethics commissioner in 2019 ruled that Mr. Trudeau tried to circumvent, undermine and discredit his former justice minister and attorney general, Jody Wilson-Raybould, in connection with a criminal case against SNC-Lavalin, a multinational engineering and construction firm based in Montreal. That same year, images surfaced of Mr. Trudeau wearing blackface or brownface as a student in the 1990s and as a teacher at a private prep school in 2001.
Infighting: Mr. Trudeau’s hold on power slipped in September when the left-leaning New Democratic Party deprived Liberals of guaranteed support needed to pass legislation. Last month, Chrystia Freeland, the deputy prime minister and finance minister, resigned abruptly, a stinging rebuke to Mr. Trudeau.
Who are the top contenders to succeed him?
Conservatives: Pierre Poilievre has led the Conservative Party since 2022, branding himself as the anti-Trudeau, practical and down-to-earth. He supported a blockade of Canada’s capital, Ottawa, in 2022 led by truckers who opposed vaccine mandates and pandemic restrictions. Mr. Poilievre has been eyeing the top government spot since at least 1999, when as a university student he wrote an essay that won a cash prize about what he would do as prime minister.
In a video posted on social media on Monday, Mr. Poilievre criticized members of Mr. Trudeau’s Liberal Party of keeping him in power only until his popularity plunged.
Liberals: After her resignation last month, there was widespread speculation that Chrystia Freeland, the former deputy prime minister and finance minister, would start her own bid to run the Liberal Party.
On Monday, Trudeau had kind words for Ms. Freeland. He declined to share the details of what transpired between them, but people familiar with the events surrounding her departure said that Trudeau attempted to fire her over a Zoom call and offered her a minister-without-portfolio position, which she declined.
Other Liberal contenders include Dominic LeBlanc, who became finance minister when Ms. Freeland resigned; Mélanie Joly, Canada’s top diplomat since 2021; and Mark Carney, the former governor of the Bank of Canada, who also led the Bank of England.
Ephrat Livni contributed reporting.
