| William Thomas Sweigert | |
| Office: | Senior Judge of the United States District Court for the Northern District of California |
| Term Start: | November 30, 1973 |
| Term End: | February 16, 1983 |
| Office1: | Judge of the United States District Court for the Northern District of California |
| Term Start1: | September 21, 1959 |
| Term End1: | November 30, 1973 |
| Appointer1: | Dwight D. Eisenhower |
| Predecessor1: | Edward Preston Murphy |
| Successor1: | William H. Orrick Jr. |
| Birth Name: | William Thomas Sweigert |
| Birth Date: | 13 October 1900 |
| Birth Place: | San Jose, California |
| Education: | University of San Francisco School of Law (LL.B.) |
William Thomas Sweigert (October 13, 1900 – February 16, 1983) was a United States district judge of the United States District Court for the Northern District of California.
Born in San Jose, California, Sweigert received an Artium Baccalaureus degree from St. Ignatius College (now the University of San Francisco) in 1921 and a Bachelor of Laws from the St. Ignatius College School of Law (now the University of San Francisco School of Law) in 1923. He was in private practice in San Francisco, California, from 1923 to 1940, and was a lecturer at the University of San Francisco School of Law from 1925 to 1932. He was an assistant state attorney general (later chief assistant attorney general) of California from 1940 to 1942, and was then executive secretary to Governor Earl Warren 1943. He was a Judge of the Municipal Court of San Francisco in 1949, and of the San Francisco County Superior Court from 1949 to 1959.
On April 23, 1959, Sweigert was nominated by President Dwight D. Eisenhower to a seat on the United States District Court for the Northern District of California vacated by Judge Edward Preston Murphy. Sweigert was confirmed by the United States Senate on September 14, 1959, and received his commission on September 21, 1959. He assumed senior status on November 30, 1973, serving in that capacity until his death on February 16, 1983.