John Jay Knox Jr. (March 19, 1828 – February 9, 1892) was an American financier and government official. He is best remembered as a primary author of the Coinage Act of 1873, which discontinued the use of the silver dollar. Knox was Comptroller of the Currency from 1872 to 1884. An advocate of uniform currency for the national banks of the country, his portrait was featured on the obverse of the $100 United States national bank notes of the Series of 1902.