Russell C. Fagg (born June 26, 1960) is an American attorney, former judge, and politician. A Republican, he served two terms in the Montana House of Representatives from 1991 to 1995. He succeeded Mary McDonough in the 89th district. Fagg was succeeded by Peggy Arnott.
Fagg was elected district judge in Yellowstone County, Montana, in 1994. He defeated the incumbent, Russell Fillner. He retired in October 2017. Fagg was succeeded by Don Harris. He was a candidate in the Republican primary for the 2018 U.S. Senate election in Montana.