William Cumback (March 24, 1829 – July 31, 1905) was an American lawyer and Civil War veteran who served one term as a U.S. Representative from Indiana from 1855 to 1857.

Born near Mount Carmel, Indiana, Cumback attended the common schools and was graduated from Miami University, Oxford, Ohio.

He was appointed a paymaster in the Army and served throughout the Civil War.

President U.S. Grant nominated Cumback as the U.S. Minister to Portugal in 1870 but he declined the appointment.

[1] This article incorporates public domain material from the Biographical Directory of the United States Congress