Marianne Borgen (born 2 June 1951) is a Norwegian politician for the Socialist Left Party, who served as Mayor of Oslo from 2015 to 2023.

She worked as a consultant in the Ministry of Local Government and Labour from 1979 to 1985, for the Ombudsman for Children in Norway from 1985 to 1995, for the County Governor of Oslo and Akershus from 1995 to 1997 and then in Save the Children in Norway.

[1][2] She served as a deputy representative to the Parliament of Norway from Oslo during the terms 1989–1993, 1993–1997, 1997–2001 and 2001–2005.

[3] In 2007, she was the Socialist Left Party's candidate to become Mayor of Oslo, without succeeding.

[5][6] In February 2022, she announced that she wouldn't be seeking re-election as mayor in 2023.