Guy Johnson (c.1740 – 5 March 1788) was an Irish-born military officer and diplomat for the Crown during the American War of Independence. He had migrated to the Province of New York as a young man and worked with his uncle, Sir William Johnson, British Superintendent of Indian Affairs of the northern colonies.
He was appointed as his successor in 1774. The following year, Johnson relocated with Loyalist supporters to Canada as tensions rose in New York before the American Revolutionary War. He directed joint militia and Mohawk military actions in the Mohawk Valley. Accused of falsifying reports, he went to London to defend himself after the war, and died there in 1788.