Dr. Sir William Beatty MD FRS (April 1773–25 March 1842) was an Irish surgeon who served in the Royal Navy. Born in Derry, Ireland, he joined as a surgeon's mate in 1791 at the age of 18. He is best known as the Ship's Surgeon on the HMS Victory during the Battle of Trafalgar, at which he witnessed the death of Admiral Horatio Nelson, and for authoring an account of that battle - The Death of Lord Nelson.
He was the eldest son of James Beatty, an officer in the Irish Revenue Service, and Ann Smyth. No records survive of his education, though he attended a local school, most likely Foyle Academy, before beginning his medical studies. He may have been apprenticed to his uncle George Smyth, a half-pay naval surgeon in nearby Buncrana, before studying at either the University of Glasgow or at the "The United Hospitals of the Borough" - the joint medical school of Guy's and St Thomas' Hospitals in London. What is known is that on 5 May 1791, the 18 year old Beatty was examined before the London Company of Surgeons, and found qualified for employment by the Navy.