Sophia Louisa Jex-Blake (1840 – 1912) was an English physician, teacher and feminist.

She was born in Hastings, the daughter of retired lawyer Thomas Jex-Blake and Mary Jex-Blake née Cubitt. In 1858 she overcame the objections of her parents and enrolled as a student at Queen's College, a teacher training college for women in London. From 1859 to 1861 she worked as a mathematics tutor at the college but had to agree not to accept a salary, due to her parent's prejudice about middle class women working.

She went on to teach in Germany and the United States of America and published a book about her experiences - A Visit to some American Schools and Colleges. She became strongly influenced by developments in co-education in the USA and met one of the country's pioneer female physicians, Dr Lucy Sewell , making the decision to switch from teaching to train as a doctor in the United States.

The death of her father in 1868 forced her to return to England to support her mother, where she found that medical schools were refusing to accept women students. Sophia Jex-Blake eventually persuaded Edinburgh University to enrol her and five other women in 1869 - the first female medical undergraduates at a British university - though they had to fund their own segregated lectures. They encountered strong opposition from male students and on 18 November 1870 a riot broke out as they arrived at Surgeon's Hall for their anatomy exam. There was further resistance from the authorities, who rendered their final examination results in 1872 void, citing university regulations that only allowed medical degrees to be awarded to men.

Sophia continued with a determined public campaign against the discrimination of British universities and the BMA. Russell Gurney , a campaigning MP who supported women's rights, took up her cause and in 1876 managed to gain support in parliament for the Enabling Act that removed restrictions on medical schools to educate and graduate women on the same terms as men.

Ironically, Sophia had failed her final papers at Edinburgh, but in 1876 she finally gained a medical degree from the University of Berne and a licentiate from the King’s and Queen’s College of Physicians of Ireland, which had just voted to admit women. The qualification of LKQCPI finally allowed her to join the medical register of the General Medical Council in 1877 - the third registered woman doctor in Britain.

Whilst awaiting qualification, Jex-Blake joined with pioneering physician Elizabeth Garrett Anderson (who had been licensed by a method since closed to women), Elizabeth Blackwell (who had qualified as a doctor in the USA) and Thomas Henry Huxley, in establishing the London Medical School for Women in 1874. However, she withdrew from involvement in this when her candidature for principal was rejected in favour of Isabel Thorpe . She moved to Edinburgh where she set up a private medical practice and in 1886 founded the Edinburgh School of Medicine for Women, which in 1894 achieved her aim of graduating women in medicine at Edinburgh.

She retired from medicine in 1899 and moved to Tunbridge Wells, but remained a strong campaigner for women's suffrage up to her death at the age of 62.

She was the sister of Thomas William Jex-Blake .