In Florence Nightingale's correspondence a series of letters to and from J.S. Mill treat a different subject than her usual correspondence with government officials, health and sanitation reformers, and hospital administrators in many parts of the world. Although it was never her intention when she initiated the exchange of letters, she and Mill quickly became involved in a controversy concerning the role of women.

Interwoven with some religious and philosophical matters, the Nightingale-Mill correspondence which falls into two periods, 1860 and 1867, is essentially a debate on women's rights. One debate concerns terminology and hinges on the entire validity of the question of publicity for the women's movement, then in its infancy, as well as the opening of the medical profession to women. The other focuses on differing perceptions of the role of women in political action. The exchange never became public during the lifetime of the participants, emerging with little notice only in the twentieth century with the complete publication of their correspondence in the journal Hospitals in 1936.

J.S. Mill's views on women's rights were public knowledge in his own day and have continued to be studied exhaustively. Florence Nightingale has been studied as the remarkable woman responsible for opening a respected profession for women. The point is often made that she refused to sign the women's petition Mill presented to the House of Commons in 1866 and would not at first become a member of the London National Society for Women's Suffrage.