Francis Geach MD, FRS was surgeon to the Royal Naval Hospital, Plymouth from about 1765 until he died in 1798. The son of a sail maker, he was born and raised in Plymouth. He was apprenticed to a surgeon in 1745 and probably undertook some medical training in London but he spent his professional career in Plymouth as a naval surgeon and in private practice. Geach had a particular interest in trauma and skin disease and was highly respected as a diagnostic physician, notably of inflammatory disorders, but he also had an interest in local issues including the cause of Devonshire colic. He was noted for the recognition of the skin disease of Francis Beaufort, later Admiral Sir Francis, as Greek leprosy (psoriasis) and for the recognition and support he gave to Sir William Knighton, physician and private secretary to the Prince Regent, later George IV. This article summarises Francis Geach's genealogy, medical and academic practice, his breadth of interests and his contribution to Devonshire life in the 18th century.