Franklin is a city in Warren County, Ohio, United States. The population was 11,771 at the 2010 census.
Franklin was founded by General William C. Schenck, in 1796. The settlement was named for Benjamin Franklin. Franklin was incorporated in 1814 and became a city in 1951.
One of the first four post offices in Warren County, Ohio was established 1 April 1805. The Franklin Post Office still stands today though on a different site from that on which it was originally built. The first postmaster was John N. C. Schenck, brother of General Schenck.