Truman Harrison Hoag (April 9, 1816 – February 5, 1870) was a U.S. Representative from Ohio.

Born in Manlius, New York, Hoag attended the public schools. He moved to Syracuse, New York, in 1832 and was employed as a clerk in a store and later in the canal collector's office. He moved to Oswego, New York, in 1839 and was employed for a commission merchants company, moving to Toledo, Ohio, in 1849 as agent of the same firm. Later became engaged in transportation and in mercantile pursuits. He also engaged in the manufacture of illuminating gas and of coke. He was an unsuccessful candidate for mayor in 1867.

Hoag was elected as a Democrat to the Forty-first Congress and served from March 4, 1869, until his death in Washington, D.C., on February 5, 1870. He was interred in Forest Cemetery in Toledo, Ohio.