She was born Millicent Garrett in Aldeburgh, Suffolk, England. As a suffragist, she took a moderate line, but was a tireless campaigner, concentrating much of her energy on the struggle to improve women's opportunities for higher education. In 1871, she co-founded Newnham College, Cambridge. She later became president of the National Union of Women's Suffrage Societies (the NUWSS), a position she held from 1897 until 1919.
In July 1901 she was appointed to lead the British Government's appointed Fawcett Commission to South Africa and investigate conditions in the concentration camps that had been created there. Her report corroborated what the campaigner Emily Hobhouse had said about conditions in the camps.
Millicent Fawcett came from a liberal family, and along with her sisters was given a good education. When she was twelve, her sister Elizabeth Garrett went to study medicine in London, later becoming the first female doctor in Britain. When Millicent was 13 Elizabeth returned home with her friend Emily Davies. Sitting by the fireside they selected careers for advancing the frontiers of women's rights, Elizabeth took Medicine, Emily took Education, and Millicent was allocated Politics and votes for women. On a visit to her sister in 1865, Millicent met John Stuart Mill, the noted philosopher of liberalism concerned with women's rights and female suffrage. He introduced Millicent to her future husband Henry Fawcett, the Liberal Member of Parliament who later became Postmaster General in Gladstone's government. They married in 1867.
Henry Fawcett was blind, and as a result Millicent acted as his secretary, often sitting in on meetings in order to transcribe them for him. As a result, she gained a knowledge of the political world. They had a daughter together, Philippa Fawcett, who was born in 1868. She also worked as a tutor at the Birkbeck Literary and Scientific Institution.
From the 1870s, Millicent campaigned for female suffrage, with her husband's backing. In 1884, Henry Fawcett died, and Millicent began to concentrate on politics. After the death of Lydia Becker, she became the leader of the National Union of Women's Suffrage Societies (NUWSS), the main suffragist organisation in Britain. She held this post until 1919, a year after the first women had been granted the vote. After that, she left the suffrage campaign for the most part, and devoted much of her time to writing books, including a biography of Josephine Butler.
She was granted an honorary LLD by St. Andrew's University in 1905, awarded a damehood (GBE) in 1925, and died four years later, in 1929. Her memory is preserved now in the name of the Fawcett Society, and in Millicent Fawcett Hall, constructed in 1929 in Westminster as a place that women could use to debate and discuss the issues that affected them. The hall is currently owned by Westminster School and is the location of its drama department, incorporating a 150-seat studio theatre.
Fawcett also campaigned for the repeal of the Contagious Diseases Acts, which reflected sexual double standards. The Acts required that prostitutes be examined for sexually transmitted diseases, and if they were found to have passed any on to their customers, they were imprisoned. Poor women could be arrested, and could also be imprisoned for refusing consent to the examination, which was invasive and could be painful. The prostitutes' infectious male customers were not subject to the Acts. The Acts were eventually repealed as a result of Fawcett's and others' campaigning.
When the First World War broke out in 1914, while the WSPU ceased all of their activities to focus on the war effort, Fawcett's NUWSS did not. This was largely because as the organisation was significantly less militant than the WSPU, it contained many more pacifists, and general support for the war within the organisation was weaker. The WSPU, in comparison, was called jingoistic as a result of its leaders' strong support for the war. While Fawcett was not a pacifist, she risked dividing the organisation if she ordered a halt to the campaign, and the diverting of NUWSS funds to the government, as the WSPU had done. The NUWSS continued to campaign for the vote during the war, and used the situation to their advantage by pointing out the contribution women had made to the war effort in their campaigns.
Fawcett is considered instrumental in 6 million British women over 30-years-old gaining the vote in 1918.