John William Clancy (February 24, 1888 – March 2, 1969) was a United States federal judge.
Born in New York City, Clancy received a B.A. from Fordham College in 1909 and an LL.B. from Fordham University School of Law in 1912. He was in private practice in New York City from 1912 to 1936.
On June 15, 1936, Clancy was nominated by President Franklin D. Roosevelt to a new seat on the United States District Court for the Southern District of New York created by 49 Stat. 1491. He was confirmed by the United States Senate on June 20, 1936, and received his commission two days later. He served as chief judge from 1956 to 1959, assuming senior status on April 3, 1959. Clancy served in that capacity until his death in New York City, in 1969.