William Balmain (2 February 1762 – 17 November 1803) was a Scottish-born naval surgeon and civil administrater who sailed as an assistant surgeon with the First Fleet to establish the first European settlement in Australia, and later to take up the appointment of the principal surgeon, for New South Wales.
Balmain was born at Balhepburn in the Parish of Rhynd, Perthshire, Scotland, to Alexander Balmain (b. 1714), tenant farmer, and his second wife, Jane Henderson. Little is known of his early life but in 1779 he was enrolled as a medical student at Edinburgh University. Next year he entered the Royal Navy to train as a Surgeon's Mate.
From November 1784 he served on Nautilus during a survey of the Das Voltas region of South West Africa (Namibia) which the British government was considering as a possible destination for the convicts then overcrowding British prisons and hulks.
On 21 October 1786 Balmain applied to join the group of officers to establish the new colony in New South Wales and was appointed third assistant surgeon to the principal surgeon, John White. Eleven ships, including six transports, carried 772 convicts, officers, marines, crews, and some wives and children, travelled more than 10,000 miles (16,000 km) to reach the unknown shore. Before the fleet sailed, Balmain correctly diagnosed a prevalent convict illness at Portsmouth. He sailed as surgeon on the convict ship Alexander. On the voyage Balmain delivered the Fleet's first child.
On arrival at Port Jackson, (Sydney Harbour) the surgeons had the difficult task of attending to the sick in tents while supervising the construction of emergency timber hospital huts.
By August 1788 tensions between Balmain and the principal surgeon, John White, became so great that they fought a duel with pistols in which Balmain received a small flesh wound in the right thigh. Ralph Clark commented "it would not have rested there had the governor not taken the matter in hand and convinced the two sons of Aescalipius that it was much better to draw blood with the point of their lance from the arm of their patients than to do it with pistol balls from each other."