John Mullanphy (1758 – August 29, 1833) was an Irish immigrant to the United States who became a wealthy merchant in St. Louis and in Baltimore.

[1] Raised by his uncle Bryan Mullanphy after his father's second marriage, at age twenty he joined the Irish Brigade of the French Army as an ensign.

While in Baltimore Mullanphy became a friend of John Carroll, the first Catholic bishop in America.

The Mullanphy family next moved to Frankfort, Kentucky in 1798 where John opened a bookstore and general merchandise store.

In 1802 he built a sailing brig on the Kentucky River at Frankfort, loaded it with produce and sent it to the West Indies under the command of a Captain Watson from Philadelphia.