John J. Kiernan (February 1, 1847 in Brooklyn, Kings County, New York - November 29, 1893) was an American politician from New York.
Kiernan began work as a messenger boy with the Magnetic Telegraph Company, and later with Western Union. In 1869, he opened his own financial news service, Kiernan Wall Street Financial News Bureau, using a stock ticker. About 1880, he hired Charles Dow and Edward Jones as financial reporters. Dow and Jones left in 1882 to found the company which would soon launch The Wall Street Journal, and Kiernan went into partnership with William P. Sullivan. Soon after the business got into trouble, and Kiernan left it in 1888.
Kiernan was a member of the New York State Senate (2nd D.) from 1882 to 1885, sitting in the 105th, 106th, 107th and 108th New York State Legislatures.
He died on November 29, 1893, of "heart failure and pneumonia".