Justin Pierre James Trudeau (born December 25, 1971) is a Canadian politician who served as the 23rd prime minister of Canada from 2015 to 2025. He led the Liberal Party from 2013 until his resignation in 2025 and was the member of Parliament (MP) for Papineau from 2008 until 2025.

Trudeau was born in Ottawa, Ontario, during the first premiership of his father, Pierre Trudeau. He attended Collège Jean-de-Brébeuf, and holds a Bachelor of Arts degree in English from McGill University and a Bachelor of Education degree from the University of British Columbia. After graduating, he taught at the secondary school level in Vancouver before returning to Montreal in 2002 to further his studies. He served as chair for the youth charity Katimavik and as director of the not-for-profit Canadian Avalanche Association. In 2006, he was appointed as chair of the Liberal Party's Task Force on Youth Renewal. Trudeau was elected to represent the riding of Papineau in the House of Commons in the 2008 federal election. He became the Liberal Party's Official Opposition critic for youth and multiculturalism in 2009 and critic for citizenship and immigration in 2010. In 2011, he was appointed as a critic for secondary education and sport. In 2013, Trudeau was elected as the leader of the Liberal Party. He led the party to a majority government in the 2015 federal election, bringing the party from a third place finish in the previous election and with the largest-ever numerical increase of seats by any party in a Canadian election. He became the second-youngest prime minister in Canadian history and the first to be the child of a previous prime minister.

Upon assuming office, Trudeau created the Canada Child Benefit, legalized medical assistance in dying, legalized recreational marijuana, advanced Senate reform through the establishment of the Independent Advisory Board for Senate Appointments, and introduced the federal carbon tax. In foreign policy, Trudeau's government resettled refugees of the Syrian civil war, signed the Paris Agreement on climate change, and negotiated trade agreements including the Canada-United States-Mexico Agreement (CUSMA) and the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP). He was found twice to be in violation of conflict of interest law by Canada's ethics commissioner—first in the Aga Khan affair, and later in the SNC-Lavalin affair.

Trudeau's Liberal Party was re-elected with a minority government in the 2019 federal election. From 2020, he led Canada through the COVID-19 pandemic and subsequent recession by enacting financial aid programs, a nationwide vaccination campaign, and military support. His government also introduced a ban on "assault-style" firearms following the 2020 Nova Scotia attacks and launched a national $10-a-day child care program. He was investigated for a third time by the ethics commissioner for his role in the WE Charity scandal, but was cleared of wrongdoing. Trudeau led the Liberals to another minority government in the 2021 federal election. He subsequently invoked the Emergencies Act for the first time in Canadian history in response to the Freedom Convoy protests; the Federal Court later ruled this action unjustified and in violation of Charter rights. In early 2022, his party entered a confidence and supply agreement with the New Democratic Party (NDP), which resulted in the Canadian Dental Care Plan and a framework for national pharmacare before the NDP withdrew from the agreement in late 2024. On the international stage, Trudeau responded to the Russian invasion of Ukraine by imposing sanctions on Russia and authorizing humanitarian and military aid to Ukraine. His premiership concluded amid a trade war with the United States, to which he responded by implementing 25% retaliatory tariffs on $30 billion worth of U.S. goods.

Following a steady decline in popular support, the sudden resignation of deputy prime minister Chrystia Freeland in December 2024 and an ensuing political crisis, Trudeau announced in January 2025 that he would resign as prime minister and leader of the Liberal Party. He advised the Governor General to prorogue Parliament until March 24, while the party held a leadership election. Trudeau remained Liberal leader until Mark Carney was elected as his replacement on March 9. He resigned as prime minister five days later and stood down as an MP at the 2025 federal election.

On June 23, 1971, the Prime Minister's Office (PMO) announced that Prime Minister Pierre Trudeau's wife of four months, Margaret Trudeau (née Sinclair), was pregnant and due in December. Justin Trudeau was born on December 25, 1971, at 9:27 pm EST at the Ottawa Civic Hospital. He is the second child in Canadian history to be born to a prime minister in office; the first was John A. Macdonald's daughter Margaret Mary Theodora Macdonald (February 8, 1869 – January 28, 1933). Trudeau's younger brothers Alexandre "Sacha" (born December 25, 1973) and Michel (October 2, 1975 – November 13, 1998) were the third and fourth.

Trudeau is predominantly of Scottish and French Canadian descent. His grandfathers were businessman Charles-Émile Trudeau and Scottish-born James Sinclair, who was minister of fisheries in the cabinet of Prime Minister Louis St. Laurent. Trudeau's maternal great-grandfather Thomas Bernard was born in Makassar, Indonesia and immigrated to Penticton, British Columbia, in 1906 at age 15 with his family. Through the Bernard family, kinsmen of the Earls of Bandon, Trudeau is the fifth great-grandson of Major-General William Farquhar, a leader in the founding of modern Singapore; Trudeau also has remote ethnic Malaccan and Nias ancestry.

Trudeau was baptized with his father's niece Anne Rouleau-Danis as godmother and his mother's brother-in-law Thomas Walker as godfather, at Ottawa's Notre Dame Basilica on the afternoon of January 16, 1972, which marked his first public appearance. and given the names "Justin Pierre James". On April 14, 1972, Trudeau's father and mother hosted a gala at the National Arts Centre, at which visiting U.S. president Richard Nixon said, "I'd like to toast the future prime minister of Canada, to Justin Pierre Trudeau" to which Pierre Trudeau responded that should his son ever assume the role, he hoped he would have "the grace and skill of the president". Earlier that day, first lady Pat Nixon had visited him in his nursery and gifted him a stuffed toy Snoopy.