John Pitcairn (1722–June 17, 1775) was a British Marine who was stationed in Boston, Massachusetts at the start of the American Revolutionary War.

John was born in late 1722 in Dysart, a port town in Fife, Scotland. His parents were the Reverand David and Katherine (Hamilton) Pitcairn. He entered the Marines, and was commission as a Lieutanant in 1746. He served in Canada during the French and Indian War as a Captain, and was promoted to Major in 1771. In 1774 he arrived in Boston, Massachusetts in command of 600 Marines to support the occupation.

Major Pitcairn was respected by the citizens in Boston as one of the more reasonable officers in the occupying force. Nevertheless, he was in command of the advance party when the first shots were fired at Lexington on April 19, 1775. Although villanized by some American accounts, his behavior that day was honorable and valiant. He had a horse shot out from under him, and even lost a pair of matched pistols when the column's baggage was abandoned. American leader Israel Putnam carried them through the rest of the war.

Trumbull's Battle of Bunker Hill.

At the Battle of Bunker Hill he commanded a reserve force of about 300 marines. They landed at the south end of the Charletown pennninsula. When the first assaults failed, he led them up the hill toward the American position, only to fall to a rifle shot. His son William was also a Royal Marine, and was present when his father was mortally wounded. John was carried back to Boston, and died of his wound within hours. He was originally buried at the Old North Church in Boston, but was reinterred at the Church of St. Batholomew the Less in London, England.

John Trumbull's famous painting of the Battle of Bunk Hill depicts his death. However, it contains several errors and anachronisms. No known picture of Major Pitcairn survives. Another son, Dr. David Pitcairn was used as a model by Trumbull, and the uniform depicted was adopted by the Marines in the 1780s. Pitcairn is shown lying at the bunker at its capture from the American force, but he was shot while starting the ascent of the hill. Pitcairn is also depicted in the scene of the Battle of Lexington in the U.S. Capital rotunda.

Pitcairn Island was named for another son, Robert, was a midshipman in the British navy. While on watch on a cruise, he was the first to sight the unknown island in 1767.