Mette Frederiksen (Danish: [ˈmetə ˈfʁeðˀəʁeksn̩] ; born 19 November 1977) is a Danish politician who has been serving as prime minister of Denmark since June 2019, and leader of the Social Democrats since June 2015. The second woman to hold either office, she is also the youngest prime minister in Danish history, the first to be born after Margrethe II's accession to the throne, and the first to serve under Frederik X.

Besides a brief career as a trade unionist (2000–2001), Frederiksen has never had any employment outside politics. She was first elected to the Folketing in the 2001 general election, representing Copenhagen County. After the Social Democrats won the 2011 general election, she was appointed Minister of Employment by Prime Minister Helle Thorning-Schmidt. She was promoted to Minister of Justice in 2014. After the Social Democrats' narrow defeat in the 2015 general election, Thorning-Schmidt stood down, and Frederiksen won the subsequent leadership election to replace her, becoming Leader of the Opposition. Frederiksen led her party into the 2019 general election, which resulted in the bloc of left-wing and centre-left parties (her Social Democrats, the Social Liberals, the Socialist People's Party, the Red–Green Alliance, the Faroese Social Democratic Party, and Greenland's Siumut and Inuit Ataqatigiit) winning a majority in the Folketing. Frederiksen was subsequently commissioned by Queen Margrethe II to lead negotiations to form a new government, and was sworn in as prime minister on 27 June. In December 2021, she became the longest-serving incumbent female head of government in the European Union.

In July 2022, the Mink Commission released a report that criticized Frederiksen's government's handling of the Cluster 5 COVID-19 outbreak among Danish mink, though it absolved Frederiksen of deliberate misleading of the public. The Radikale Venstre brought an ultimatum against Frederiksen threatening to bring a motion of no confidence against her government if she did not call for an early election. On 5 October 2022, Frederiksen announced that an election was to be held on 1 November of the same year. The election resulted in the best result for the Social Democrats in 20 years with the party gaining two more seats for a total of 50. Frederiksen herself received 60,837 votes, the most of any candidate. On 13 December 2022, Frederiksen announced that an accord on a coalition government with the Social Democrats, the Venstre and the Moderates had been reached, with herself continuing as prime minister.