MacCormac, Sir William (1836–1901), surgeon, was born 17 January 1836 in Belfast, son of Henry MacCormac (qv), physician, and Mary MacCormac (née Newsham). Initially educated at the Royal Belfast Academical Institution, he later studied in Dublin and Paris, before entering QCB (October 1851) as an engineering student. He transferred to the arts course, graduating BA (1855) and MA (1858). Awarded a scholarship in natural philosophy (1856), he graduated MD (1857), subsequently being awarded an honorary M.Ch. (1879) and an honorary D.Sc. (1882) by QCC.
After further studies in Berlin, he became a licentiate of the RCSI (1857) and a fellow of the RCPI (1864). From 1864 to 1870 he worked as a general practitioner in Belfast and also served as a surgeon and lecturer on clinical surgery at the Royal Hospital. In 1870 he set up practice in Harley St., London, and, after the outbreak of the Franco–Prussian war, went to Paris, where he volunteered his services to the French National Society for Aid to the Wounded. He was sent to Metz on 9 August 1870 but ordered back to Paris as a suspected spy on 11 August, leaving Metz on one of the last trains before it was invested by the Prussian army. On his return to Paris he joined the Anglo-American ambulance corps and was posted to Sedan; arriving there, his party took possession (31 August) of the Caserne d'Asfeld, a barracks that had been converted into a hospital. He tended the wounded from the battle of Sedan (1 September 1870) and remained in the town after its occupation by the Prussians, cooperating with Prussian surgeons in operations on the wounded of both armies. He did object, however, to the Prussian medical services moving French wounded from the improvised hospital at the district public school, as he saw this as a breach of the Geneva code.
Returning to London after the war, he became (1871) a fellow of the Royal College of Surgeons, and was appointed assistant surgeon at St Thomas's Hospital. In 1873 he was made a full surgeon and lecturer in surgery at St Thomas's, and in 1876 became chief surgeon to the National Aid Society for the Sick and Wounded during the Turco–Serbian war. In 1880 he was elected president of the London Medical Society, and in 1881 was honorary general secretary of the International Medical Congress in London. Knighted in December 1881, he later served as an examiner in surgery at the University of London and also for the naval, military, and Indian medical services. In 1883 he was elected a member of the council of the RCS, and was appointed to the board of examiners in 1887. Elected president of the RCS in 1896, he was reelected on four successive occasions, which was unprecedented. Created a baronet in 1897, he was appointed as surgeon in ordinary to the prince of Wales (later Edward VII), and in September 1898 was made a KCVO. During the second Boer war he served as consulting surgeon to the British army in South Africa, visiting hospitals in Natal and the Cape Colony. In June 1900 he was awarded the honorary degrees of MD and M.Ch. by Dublin University; he was created a KCB in 1901 in recognition of his services in South Africa, and was awarded several foreign orders, including the French Légion d'honneur, and also became an honorary member of the Academy of Medicine of Paris.
During the course of his career, he published several works, including Antiseptic surgery (1880) and Surgical operations (pt I, 1885; 2nd ed., 1891; pt II, 1889). He contributed an article to the Graphic's history of the South African war (1900), and several articles to the Dublin Quarterly Journal of Medical Science. He married (1861) Katherine Maria Charters of Belfast; they had no children. He died 4 December 1901 and was buried at Kensal Green cemetery, London.