James Thacher (February 14, 1754 – May 26, 1844) was an American physician and writer, born in Barnstable, Mass. When Thacher was 16 he became an apprentice for Abner Hersey, a doctor from Barnstable, Mass. From 1775 to 1783 he was a surgeon in the Revolution, in the Massachusetts 16th Regiment. Afterward, he practiced in Plymouth, Mass. until his death.
He was married to Susannah Hayward of Bridgewater, Massachusetts. They had six children. However only two daughters lived into adulthood.
Thacher was stationed at West Point in 1780 and supported the execution by George Washington of the British spy John André. He was the author of Military Journal during the American Revolutionary War (1823); Observations Relative to the Execution of Major John André as a Spy in 1780 (1834); American New Dispensatory (1810; fourth edition, 1821); and other books.