James Johnstone (c. 1759 – 1823) was a British naval officer and explorer. He is noted for having served as sailing master of the armed tender HMS Chatham and later acting lieutenant during George Vancouver’s 1791-95 expedition to the Pacific Northwest.Johnstone Strait in British Columbia is named after him.
Johnstone joined the navy early in 1779, serving aboard the ships HMS Keppel (a 14-gun sloop), HMS La Fortune (a recently captured French frigate), HMS Formidable, HMS Queen, and HMS Assistance; during this time he sailed to New York, the West Indies (several times), and participated in the Battle of the Chesapeake. On the last ship he met Archibald Menzies, whom Johnstone would become lifelong friends with. He was appointed master in 1785, receiving his master's certificate the following year. Both he and Menzies were discharged in August 1786. Despite passing his lieutenant’s examination the next month, he wouldn't receive his commission until seven years later.
In October 1786 Johnstone left Britain as mate of the Prince of Wales under James Colnett on a voyage to the Northwest coast of North America in search of sea otter. Menzies accompanied him. In January 1789 in Macau, when Colnett decided to take another ship, the Argonaut, back to the Northwest coast, Johnstone assumed command of the Prince of Wales. He sailed the ship back to Britain, which he reached in July.