Luke Day Jr. (July 21, 1743 – June 1, 1801) was an American military officer, revolutionary, and farmer, most well known for his leadership role in Shays' Rebellion, for which he was convicted of high treason and sentenced to death, before being pardoned by Governor John Hancock. He was referred to as the "Master Spirit" of the insurrection, and was only passed over as overall leader in favor of Daniel Shays due to the perception of overzealousness on his part, by his men.