Marsh, Sir Henry (1790–1860), physician, was born in Loughrea, Co. Galway, into a distinguished clerical family, descendant of the protestant archbishop Francis Marsh (qv), and son of the Rev. Robert Marsh, rector of Killinane, Co. Galway, and of Sophia Marsh (née Wolseley; d. c.1791), granddaughter of Sir Thomas Molyneux (qv). Educated at a classical school in Loughrea and at home from the age of 12, he entered TCD and graduated BA (1812). As a student he became a member of the Church of God, a sect founded by John Walker (qv) which was critical of the government of the established church. Despite his father's disappointment, Marsh rejected the ministry in favour of surgery.
Apprenticed (1813) to his cousin, surgeon-general (Sir) Philip Crampton (qv) at the Meath Hospital, Dublin, he studied at the RCSI and the Peter St. Medical School (later the Ledwich School). After a dissection injury and the loss of a right forefinger, he turned to medicine and was admitted licentiate (1818) of the (R)K&QCPI. He studied at La Charité in Paris and, returning to Dublin, was appointed assistant physician (1820) to his cousin, John Crampton (c.1768–1840) at Dr Steevens' Hospital, and was subsequently elected governor (1833), senior physician (1840), and visiting physician (1856). Respected for his profound knowledge, accuracy in diagnosis, and gentleness, Marsh became one of the leading physicians in Ireland. He was appointed consulting physician to the (Royal) City of Dublin Hospital on its foundation (1832), to St Vincent's Hospital, and to the Rotunda Hospital, and served on the staff of the National Infirmary and Dispensary from 1853.
A prominent figure in the Irish school of medicine, he was involved in many new developments. He was a founder (1821) of the Institution for Diseases of Children, which was established at the rear of his house in Molesworth St., before moving to Pitt (later Balfe) St. The first hospital of its kind in these islands, it provided free treatment for patients, gave clinical instruction to medical students, and educated mothers in the care of their children in health and sickness. In 1831 it treated more than 21,000 children. It subsequently merged with the National Orthopaedic and Children's Hospital to become the National Children's Hospital, Harcourt St.
Marsh was a founder (1824) and professor in the practice of medicine (1824–8) at the Park St. (later Lincoln Place) School of Medicine, and at the RCSI (1828–32), where he lectured on the diseases of children, resigning his chair to concentrate on a large and fashionable private practice. He gained a reputation as a notable lecturer and clinical teacher, publishing his lectures in the Dublin Medical Press; his Clinical lectures, edited by J. S. Hughes, were published posthumously (1867). He was also one of the six founding presidents of the pioneering Pathological Society of Dublin (1838). Established to promote the study of pathological anatomy particularly in relation to diagnosis and treatment of disease, it became famous and was the forerunner of similar societies around the world. He published papers in the Dublin Hospital Reports and the Dublin Journal of Medical Science.
Marsh received many honours: appointed physician-in-ordinary to the queen in Ireland (1837), he was created a baronet (1839); was conferred with an MD (1840) from Dublin University; was elected hon. fellow (1831) and subsequently fellow (1839) of the K& QCPI; and was three times (1841, 1845, 1857) elected to its biennial presidency. He contributed £200 towards the building of the college hall in Kildare St. Elected MRIA (1826) and vice-president of the Royal Geological Society of Ireland, he was a member of the RDS and supported the Medical Benevolent Fund of Ireland.
A popular member of high society in Dublin, Marsh was a founding member in 1856 of the revived Medical Society, a peripatetic dining club. According to Lombe Atthill (qv), he was fond of show: he kept handsome horses, had the best whip in Ireland as coachman, and sped through the streets at a great pace. He owned Kirrakill Castle, Co. Kilkenny, and houses in Knockmaroon, Co. Dublin, and at 9 Merrion Square, Dublin, where he died 1 December 1860; he was buried in Mount Jerome cemetery, Dublin. His statue by J. H. Foley (qv), unveiled in 1866, was one of four placed in the entrance hall of the (R)K&QCPI.
Marsh twice married widows: first (1820) Anne Arthur (née Crowe; d. 1846); they had a son, Henry Marsh (1821–68), who became colonel of the 3rd Regiment of Dragoon Guards. After the death of his first wife, he married (1856) Mary Henrietta Kemmis (née Jelly); they had no children.