Josephine Letitia Denny Fairfield CBE (10 March 1885 – 1 February 1978) was a medical doctor, a lawyer, a war-worker, and the first ever female Chief Medical Officer for London. She received a CBE for her outstanding achievements in medicine following her contributions in World War I, despite initially having been rejected by the War Office. Fairfield went on to work for the London County Council, where she campaigned for the initiation of new Public Health departments relating in particular to women's and children's health, and defending who she believed were the most vulnerable members of society. She was a feminist and a Fabian, and during her later life became a convert to Roman Catholicism and a believer in witchcraft.