William Carey Mathes (December 17, 1899 – July 24, 1967) was a United States federal judge.
Born in Hale Center, Texas, Mathes received a B.M.A. from the University of Texas in 1921 and an LL.B. from Harvard Law School in 1924. He was in private practice in Los Angeles, California from 1924 to 1945.
Mathes was a federal judge on the United States District Court for the Southern District of California. Mathes was nominated by President Harry S. Truman on September 24, 1945, to a seat vacated by Ralph E. Jenney. He was confirmed by the United States Senate on October 11, 1945, and received his commission on October 17, 1945. He served as chief judge from 1964-1965. He assumed senior status on June 9, 1965. Mathes served in that capacity until July 24, 1967, due to his death.