John Joseph Phelan Jr. (May 7, 1931 – August 4, 2012) was an American financier who served as president and later chairman and chief executive of the New York Stock Exchange, where he introduced computerized trading technology.

Phelan's leadership tenure at the NYSE included the 1987 stock market crash, during which he declined to halt trading.

He started college in 1949, but left after two years to serve in the US Marine Corps.

After returning from the Marines, Phelan went to work as a floor trader with his father's firm, Phelan & Co. and attended Adelphi University, where he received a bachelor's degree in business administration.

[1] John Phelan Jr. died on August 4, 2012, in Manhattan, New York City at age 81 from cancer.