Born in Cong, Co. Mayo, Kathleen Lynn (M.B., B.Ch., B.A.O., (R.U.I. 1899). F.R.C.S.I. (1909)) was the daughter of a Canon of the Church of Ireland. She was educated in England and in Dusseldorf, and at Alexandra College, Dublin. In 1899 she took her degree in the Royal University of Ireland, one of the first women to graduate in medicine. Elected House Surgeon to the Adelaide, she was opposed by medical staff on the grounds that, in failing to be a man, she was guilty of being a woman. Her appointment was not ratified. Despite the rebuff, she became a Fellow of the Royal College of Surgeons in 1909 and began a practise, which took her to the slums of Dublin and, in time, to the ranks of the Irish Citizen Army. A long-standing commitment to the Women's Suffrage Movement drew her to republican ideals, and in the course of the Lock-Out in 1913, she became a member of the ICA, organising ambulance and first aid instruction at Liberty Hall. On Easter weekend, 1916, Dr Kathleen Lynn, Chief Medical Officer of the ICA, was promoted to the rank of Captain and on Easter Monday was arrested and held in custody until her deportation to England in June 1916. By 1917 she had been released and was elected a member of the Standing Committee of Sinn Fein. Following the general round up of Sinn Fein leaders in 1918 and having been 'on the run' for some time, she appeared at the Sinn Fein Convention and then inserted a notice in the daily press indicating that she had retired to her residence at 9 Belgrave Road, Rathmines. She was arrested, but when the Lord Mayor of Dublin made representations on her behalf 'with a view to having her professional services made available during the influenza epidemic', she was duly released.

Continuing as a member of Sinn Fein, she was elected as Vice President for the IWWU, and, with Madeline ffrench-Mullen, also of the IWWU, cared for influenza victims in a disused building in Charlemont Street, once a shooting lodge of the Earl of Charlemont. Inspired by the work of the Inginini, and the brute reality that 164 out of every 1000 Dublin infants died each year from preventable diseases, Kathleen Lynn resumed her calling with militancy of a quite different order. In 1919, with their combined resources of £70, Captain Lynn and Sergeant ffrench-Mullen cleaned the lodge and launched Teach Ultan, a hospital 'for the medical treatment of infants under one year of age'. With due deference to her treatment by the medical masters of the Adelaide, she was 'adamant that the staff of St Ultan's would be confined to women medicals only'. It was, and became the front line in the battle against infant mortality, providing the opportunity for Dr Dorothy Price to continue her researches on childhood tuberculosis, leading to the establishing of the BCG unit at the hospital. Although, as Senior Physician, Dr Lynn visited the Hospital on a daily basis, she was elected to the Dail as member for Sinn Fein in 1923. In keeping with Sinn Fein's abstentionist policy she did not take the seat, but continued as an active member of Rathmines Urban District Council. As a daughter of the Manse she had, as a colleague recalled, 'a chauffeur and an enormous car' at her disposal - it was totally in character that Dr Kathleen Lynn, Fellow of the Royal College of Surgeons, exercised her own preference for the bicycle.