Margret Mari Power (1912 or 1913 – 24 June 1936) was a British political activist.
She spent time attending the Sorbonne, and then worked for the League of Nations in Geneva.
Both were supporters of the Labour Party, and tossed a coin to decide who would stand in Hornsey at the 1935 United Kingdom general election.
Mari won the coin toss, becoming the youngest woman to stand for parliament anywhere in the country, and Ivan Power worked as her deputy agent.
Although she lost the election by more than 20,000 votes, it was the strongest Labour performance in the seat to date.