| William J. Barker | |
| Office: | Senior Judge of the United States District Court for the Southern District of Florida |
| Term Start: | April 30, 1959 |
| Term End: | April 13, 1968 |
| Office1: | Chief Judge of the United States District Court for the Southern District of Florida |
| Term Start1: | 1955 |
| Term End1: | 1959 |
| Predecessor1: | John W. Holland |
| Successor1: | George William Whitehurst |
| Office2: | Judge of the United States District Court for the Southern District of Florida |
| Term Start2: | February 5, 1940 |
| Term End2: | April 30, 1959 |
| Appointer2: | Franklin D. Roosevelt |
| Predecessor2: | Alexander Akerman |
| Successor2: | William McRae |
| Birth Name: | William Julius Barker |
| Birth Date: | 25 June 1886 |
| Birth Place: | Marietta, Georgia |
| Education: | Fredric G. Levin College of Law (LL.B.) |
William Julius Barker (June 25, 1886 – April 13, 1968), frequently known as W. J. Barker,[1] was an American lawyer and United States district judge of the United States District Court for the Southern District of Florida.
Born on June 25, 1886, in Marietta, Georgia, Barker attended the Fredric G. Levin College of Law at the University of Florida and received his Bachelor of Laws in 1916. Barker was in private practice in Jacksonville, Florida from 1916 to 1925, and was a circuit court judge in Highlands County, Florida from 1925 to 1940.
President Franklin D. Roosevelt nominated Barker to the United States District Court for the Southern District of Florida on January 11, 1940, to the seat vacated by Judge Alexander Akerman. Confirmed by the Senate on February 1, 1940, he received his commission on February 5, 1940. Barker served as Chief Judge from 1955 to 1959. He assumed senior status on April 30, 1959, and remained on the court until his death on April 13, 1968.