| William Thomas Hart | |
| Office: | Senior Judge of the United States District Court for the Northern District of Illinois |
| Term Start: | June 1, 1996 |
| Term End: | January 17, 2023 |
| Office1: | Judge of the United States District Court for the Northern District of Illinois |
| Term Start1: | April 21, 1982 |
| Term End1: | June 1, 1996 |
| Appointer1: | Ronald Reagan |
| Predecessor1: | John Powers Crowley |
| Successor1: | Rebecca R. Pallmeyer |
| Birth Date: | 4 February 1929 |
| Birth Place: | Joliet, Illinois, U.S. |
| Death Place: | Chicago, Illinois, U.S. |
| Education: | Loyola University Chicago (JD) |
| Allegiance: |  United States |
| Serviceyears: | 1951–1953 |
William Thomas Hart (February 4, 1929 – January 17, 2023) was a United States district judge of the United States District Court for the Northern District of Illinois.
Born in Joliet, Illinois, Hart received a Juris Doctor from Loyola University Chicago School of Law in 1951. He was in the United States Army from 1951 to 1953. He was an assistant United States attorney of the Northern District of Illinois from 1954 to 1956. He was in private practice in Chicago, Illinois from 1956 to 1982. He was a special assistant state attorney general of Illinois from 1957 to 1958. He was a special assistant state's attorney of Cook County, Illinois in 1960.[1]
Hart was nominated by President Ronald Reagan on March 11, 1982, to a seat on the United States District Court for the Northern District of Illinois vacated by Judge John Powers Crowley. He was confirmed by the United States Senate on April 20, 1982, and received his commission on April 21, 1982. He assumed senior status on June 1, 1996, a position he held until his death on January 17, 2023.[1]