James Gideon Monahan (January 12, 1855 - December 5, 1923) was a U.S. Representative from Wisconsin.
Born at Willow Springs, near Darlington, Wisconsin, Monahan attended the common schools and was graduated from the Darlington High School in 1875. He taught school. He studied law. He was admitted to the bar in 1878 and commenced practice in Mineral Point, Wisconsin. He returned to Darlington in 1880. He served as district attorney of Lafayette County 1880-1884. He was editor and owner of the Darlington Republican Journal 1883-1919. He served as delegate to the Republican National Convention in 1888. He served as collector of internal revenue for the second Wisconsin district 1900-1908.
Monahan was elected as a Republican to the Sixty-sixth Congress (March 4, 1919-March 3, 1921). He was an unsuccessful candidate for renomination in 1920 to the Sixty-seventh Congress. He died in Dubuque, Iowa, December 5, 1923. He was interred in Union Grove Cemetery, Darlington, Wisconsin.