John Lorimer (1732–1795) was an American surgeon, mathematician, politician and cartographer in the 18th century.
Lorimer served as a surgeon for the British army in North America between 1758 and 1784, participating in both the French and Indian War and the American Revolution.
He was a fellow of the Royal College of Physicians of Edinburgh, and author of the book A Concise Essay on Magnetism; with an Account of the Declination and Inclination of the Magnetic Needle; and an Attempt to ascertain the Cause of the Variation thereof, published in 1795.
He went along with George Gauld and Thomas Hutchins not only because he was a surgeon, but also because his mathematical skills for determining latitude and longitude were greatly desired.
He used and re-published much of the written materials and charts produced by Lorimer, Gauld and Lieutenant Philip Pittman under his own name.