Thomas Roberts McMillen (June 8, 1916 – September 16, 2002) was a United States federal judge.
Born in Decatur, Illinois, McMillen received an A.B. from Princeton University in 1938 and an LL.B. from Harvard Law School in 1941. He was in the United States Army during World War II, from 1941 to 1945. He was in private practice in Chicago, Illinois from 1946 to 1966. He was a judge on the Cook County Circuit Court, Illinois from 1966 to 1971. He was in private practice in Chicago, Illinois from 1985 to 2002.
McMillen was a federal judge on the United States District Court for the Northern District of Illinois. McMillen was nominated by President Richard Nixon on March 29, 1971, to a seat vacated by William Joseph Campbell. He was confirmed by the United States Senate on April 21, 1971, and received his commission on April 23, 1971. He assumed senior status on December 31, 1984. McMillen served in that capacity until September 8, 1985, due to retirement.
He died in Evanston, Illinois.