Marie Cinq-Mars was borough mayor of Outremont from 2007 to 2017. She is a former member of the Union Montreal municipal political party. Cinq-Mars was first elected as a city councillor with the former city of Outremont in 1999. Following Outremont's merger with Montreal, she was then elected as a city councillor representing the borough of Outremont in 2002. She sat on the city of Montreal's executive committee where she was responsible for the portfolios of culture, heritage, design and the status of women.