John Fontaine Keenan (born 1929 in New York, NY) is a federal judge for the United States District Court for the Southern District of New York. Judge Keenan received a B.B.A. from Manhattan College in 1951 and an LL.B from Fordham University School of Law, in 1954. He was nominated to the court by Ronald Reagan on September 13, 1983, to a seat vacated by Lloyd F. MacMahon, confirmed by the United States Senate on September 20, 1983, and received his commission on September 20, 1983. He assumed senior status on December 31, 1996.