Robert Firth (May 12, 1918 – January 4, 1984) was a United States federal judge.
Born in Harrison, New Jersey, Firth received an A.B. from Indiana University in 1940 and was in the United States Navy Lieutenant during World War II, from 1941 to 1945. He received an LL.B. from Harvard Law School in 1948. He was a U.S. Naval Reserve Lieutenant from 1946 to 1952. He was in private practice in Los Angeles, California from 1949 to 1950. He was in private practice in Pomona, California from 1950 to 1967. He was a judge on the Los Angeles Superior Court, California from 1967 to 1974. He was a Lecturer, LaVerne College of Law, LaVerne, California from 1971 to 1973.
Firth was a federal judge on the United States District Court for the Central District of California. Firth was nominated by President Richard Nixon on February 6, 1974, to a seat vacated by Charles H. Carr. He was confirmed by the United States Senate on March 1, 1974, and received his commission on March 8, 1974. He assumed senior status on October 31, 1979. Firth's served in that capacity until January 4, 1984, due to his death.