Marion Helen Bryden (born April 2, 1918 in Winnipeg, Manitoba) is a former politician in Ontario, Canada. She was a New Democratic Party member of the Legislative Assembly of Ontario from 1975 to 1990.

Bryden was educated at the University of Manitoba, the University of Toronto and the Ontario College of Education . She has been a member of the Canadian Council of Social Development, the Elizabeth Fry Society, and the Federation of Ontario Naturalists. Bryden was also active as a union organizer, and as a researcher and statistician for the Canadian Tax Federation. During the 1960s, she served as president of the Ontario Woodsworth Memorial Foundation. Her husband, Kenneth Bryden , was a member of the Ontario Legislature from 1959 to 1967.

Marion Bryden was first elected to the Ontario legislature in the 1975 provincial election, defeating incumbent Progressive Conservative Thomas Wardle by almost 3,000 votes in the riding of Beaches—Woodbine . She defeated Wardle again by a narrower margin in the 1977 election. In the 1981 provincial election, Bryden defeated Progressive Conservative Paul Christie by only 324 votes amid provincial setbacks for the NDP.

Bryden defeated Christie again by a much greater margin in the 1985 provincial election, and won without difficulty for the redistributed riding of in the 1987 election. She retired prior to the 1990 election, at age seventy-two. The Beaches—Woodbine riding, now renamed as Beaches—East York , has remained in NDP hands since that time with Bryden being succeeded by Frances Lankin and then Michael Prue.

From 1985 to 1990, Bryden served as her party's critic for Colleges and Universities, the Solicitor-General, Correctional Services, Seniors' Issues, Revenue and Transport. She was known as an effective constituency representative.