William Medill (1802 or 1803 - September 2, 1865) was a Democratic politician from Ohio. He served as the 22nd Governor of Ohio.

Born in New Castle County, Delaware, Medill was elected to the Ohio House of Representatives, where he served from 1835-1838, serving as Speaker of the House from 1836-1837. He was elected to the United States House of Representatives in 1838, serving from 1839-1843. He lost a bid for a third term in 1842. After briefly serving as the second assistant postmaster general, Medill was appointed by President Polk as Commissioner of Indian Affairs. He returned to Ohio in 1850 to serve as the President of the 1850-1851 Constitutional Convention. Elected to the new post of Lieutenant Governor of Ohio in 1851, Medill entered office in 1852, serving until the resignation of Governor Reuben Wood on July 13, 1853 to take up a Consular office in Chile. Medill was re-elected in his own right in 1853, but was defeated in a bid for a second full term in 1855 by the anti-slavery Salmon P. Chase.