John Langdon (born June 26, 1741, Portsmouth, N.H., U.S.—died Sept. 18, 1819, Portsmouth) was a state legislator, governor, and U.S. senator during the Revolutionary and early national period (1775–1812). After an apprenticeship in a Portsmouth countinghouse and several years at sea, he became a prosperous shipowner and merchant. During the war he organized and financed John Stark’s expedition against British Gen. John Burgoyne (1777). He was a member of the Continental Congress (1775–76, 1783–84), of the New Hampshire legislature (1777–82, 1801–15), and of the state senate (1784–85). He was president of New Hampshire (1785–86, 1788–89), a delegate to the Federal Constitutional Convention of 1787, and a U.S. senator (1789–1801). In the Senate he identified himself with the followers of Thomas Jefferson but declined any national office. Later he served as governor of New Hampshire (1805–09, 1810–12).