William Joseph Nealon Jr. (born July 31, 1923) is a United States federal judge.
Born in Scranton, Pennsylvania, Nealon was a First Lieutenant in the United States Marine Corps during World War II, from 1942 to 1945. He received a B.S. from Villanova University in 1947 and an LL.B. from Catholic University of America School of Law in 1950. He was in private practice in Scranton, Pennsylvania from 1951 to 1960, also lecturing at the University of Scranton from 1951 to 1959. He was a hearing examiner for the Pennsylvania Liquor Control Board from 1955 to 1959. He was a judge on the Lackawanna County Court of Common Pleas from 1960 to 1962.
On December 13, 1962 Nealon received a recess appointment from President John F. Kennedy to a seat on the United States District Court for the Middle District of Pennsylvania vacated by John W. Murphy. Formally nominated on January 15, 1963, Nealon was confirmed by the United States Senate on March 15, 1963, and received his commission on March 27, 1963. He served as chief judge from 1976 to 1989, assuming senior status on January 1, 1989. The William J. Nealon Federal Building and United States Courthouse, located in Scranton, is named in his honor.