Feminist and pacifist. Born in Edinburgh, the only daughter of Jessie Chrystal Finlayson and John Macmillan, a tea merchant, Macmillan went to school in St. Andrews and completed her education at the University of Edinburgh, where she was the first female science graduate in 1896. She went on to study law.
In 1908, Macmillan became the first woman to address the House of Lords where she appealed for female suffrage as part of a legal case brought by a group of female university graduates. She was a founder of the Women's International League for Peace and Freedom and was a prime mover in the International Women's Congress held at The Hague in 1915, which focussed on trying to bring about a negotiated peace in the First World War. She was a delegate at the Paris Peace Conference in 1919.
Macmillan stood as the Liberal candidate for the seat of Edinburgh North in 1935, but was not elected.
She died at her home in Marchmont district of Edinburgh and was cremated, with her ashes interred in her parent's grave at Corstorphine Old Parish Church, where there is a stained glass window dedicated to her parents. Her name is commemorated by the University of Edinburgh in the Chrystal Macmillan Building on George Square.
