Seth Thomas (May 18, 1873 – February 2, 1962) was a United States federal judge. Born in McConnelsville, Ohio, he did not get a college degree until he was 31, receiving a Ph.B. from the University of Iowa in 1904. He remained at the University of Iowa for his graduate work, receiving a master's degree in 1906 and a law degree in 1910. Upon receiving his law degree, he started a private practice of law in Fort Dodge, Iowa.
Thomas suspended his private practice to become the Assistant United States Attorney for the Northern District of Iowa in 1914. After about six years of service, he returned to his private practice in 1920. He didn't return to public service until the Democratic Party again controlled the White House in 1933, when he became Solicitor for the United States Department of Agriculture.
On November 30, 1935, Charles Breckenridge Faris retired as judge of the United States Court of Appeals for the Eighth Circuit. On December 2, President Franklin D. Roosevelt put Thomas in Faris' seat via a recess appointment. On January 6, 1936, after Congress reconvened, Roosevelt nominated Thomas to a permanent appointment as judge of the Eighth Circuit. Thomas was confirmed on January 22 and received his commission on January 28.
After eighteen years of serving on the federal bench, Thomas assumed senior status on May 1, 1954. He died, still a senior judge, in Sioux City, Iowa on February 2, 1962.