Henry Duncan (24 November 1735 – 7 October 1814) was an officer of the Royal Navy, who saw service in the American War of Independence. Duncan was born in Dundee, Scotland to Alexander Duncan, Town Clerk of Dundee, and Isobel Crawford.
Duncan began his sea life in the merchant service, possibly in that of the East India Company, but entered the Royal Navy on in 1755 joining HMS Nassau. Duncan later joined HMS Newark. On 3 January 1759, Duncan passed his examination for lieutenant and joined HMS America. Duncan then joined HMS Prince in Gibraltar, but was soon transferred to HMS Namur and then HMS Barfleur.
He married Mary French in Dartmouth, on 27 November 1761. He participated in the capture of Havana in 1762 and was moved to HMS Temeraire. During this time he had two children, Isabella (born 23 August 1764) and Arthur French (born 9 February 1769). Duncan already had an older son, Henry, who later served in the Navy from 1781 until being lost off the coast of Newfoundland in 1802 with HMS Scout.
On 26 May 1768, Duncan was promoted to commander and joined HMS Wasp. Soon after he was promoted to captain. In January, 1776, William Howe was appointed as Commander-in-Chief of British forces in North America and chose Duncan to join him as flag captain of HMS Eagle. His career in North America lasted for the next six to seven years. On the commands of General Howe, Duncan commanded an invasion fleet of 26 ships carrying 2,000 men led by General William Tryon from New York to Westport, Connecticut to raid Continental Army supply depots in Danbury, Connecticut on 22 April 1777, resulting in the Battle of Ridgefield.