Guy Mark Gillette (February 3, 1879 - March 3, 1973) was a Democratic United States Senator and Representative from Iowa.
Born in Cherokee, Iowa, he attended public school and graduated from the law department of Drake University in Des Moines in 1900. He was admitted to the bar in 1900 and commenced practice in Cherokee. During the Spanish-American War, he served as a sergeant in the Fifty-second Iowa Regiment in the United States Army.
Later he engaged in agricultural pursuits and was the city attorney of Cherokee in 1906-1907. He became the prosecuting attorney of Cherokee County from 1907-1909 and a member of the State senate 1912-1916.
During the First World War, he served as a captain in the United States Army. He was elected as a Democrat to the Seventy-third Congress and reelected to the Seventy-fourth Congress, serving from March 4, 1933 until his resignation on November 3, 1936 having been elected to the United States Senate on November 3, 1936 to fill the vacancy caused by the death of Richard Louis Murphy during the term ending January 3, 1939. He was reelected in 1938 and served to January 3, 1945, failing to be reelected in 1944.
He was the chairman of the Surplus Property Board in 1945, president of the American League for a Free Palestine from 1945 to 1948. He was again elected to the United States Senate in 1948 and until January 3, 1955, once again failing to be reelected in 1954. He was a counsel with the Senate Post Office and Civil Service Committee (1955-1956) and the Senate Judiciary Committee (1956-1961).
He retired and resided in Cherokee, Iowa until his death March 3, 1973 and was interred in Oak Knoll Cemetery.