Catherine Fournier (born 7 April 1992) is a Canadian politician, who was elected as mayor of Longueuil on November 7, 2021. She is the third female mayor in the city's history.

She was previously member of the National Assembly of Quebec, having been elected in a by-election on December 5, 2016 at the age of 24.^[3] She represented the electoral district of Marie-Victorin. Fournier was the youngest member of the National Assembly, and the youngest woman ever elected to that body.^[4]

Originally elected as a member of the Parti Québécois, Fournier won a full term in 2018 even amid the PQ's meltdown in Greater Montreal; she was the only surviving PQ member from the metro area. However, she quit the PQ on March 11, 2019 to sit as an independent MNA. She believed the party had lost its way ideologically, though she still considers herself a committed sovereigntist.^[5][6]

Before her election to the National Assembly, Fournier ran for the Bloc Québécois in the 2015 federal election in the riding of Montarville, finishing second. After her defeat, she was named as the party's vice-president. A few weeks later, Fournier left the Bloc Quebecois position to join Parti Quebecois as a political attaché of PQ leader Pierre Karl Péladeau.^[7]

Fournier was born in Sainte-Julie, Quebec on 7 April 1992. She holds an economics major and political science minor from the Université de Montréal. She was a political blogger and columnist for 103.3 FM.^[2]

In 2023, Fournier revealed she had been the victim of sexual assault by Harold Lebel, a former Quebec MNA. The assault took place during the evening of October 20, 2017, while Fournier and Lebel, who were PQ MNAs at that time, were in Rimouski to introduce their party's plan to combat poverty.^[8]

In 2022, Lebel was found guilty of sexual assault by a jury and sentenced to 8 months in prison.^[9] The identity of the victim had been under a publication ban, but Fournier requested that the ban be lifted in 2023.^[8]