John Barclay (Ballyshannon, Ireland, January 22, 1749 – September 15, 1824, Philadelphia, Pennsylvania) was an American soldier, politician, and jurist. He was a member of the Constitutional Convention of 1790 and served as mayor of Philadelphia in 1791. He served in the Continental Army during the American Revolution. He enlisted in 1775 and was commissioned an ensign in 1776; he was eventually promoted to lieutenant and captain, retiring in 1782. He was appointed a Justice of the Peace in 1782 and rose to President Judge of the Courts of Bucks County in 1789.