Answer: Nancy Astor (1879-1964)
Nancy Astor (1879-1964) was an American society hostess who in 1919 was promoted as a stop-gap candidate for her husband's former seat, Plymouth Sutton. She won and held the seat for the Conservatives for more than 25 years.
Although Nancy Astor was the first woman to take her seat in parliament, the first woman to be elected to the Commons was Constance Markievicz, in the general election of 1918. However, as a member of Sinn Fein, Markievicz refused to take her seat in Parliament.
Image: A black-and-white photograph of Nancy Astor