Ralph Plumb (March 29, 1816 – April 8, 1903) was a U.S. Representative from Illinois.

Ralph Plumb was born in Busti, New York on March 29, 1816.

Deciding to study law, he was admitted to the bar in 1857 and commenced practice in Oberlin, Ohio.

During the Civil War served in the Union Army as captain and quartermaster of Volunteers, 1861–65.

Plumb engaged in banking until his death in Streator on April 8, 1903.