Millfield is a census-designated place in northern Dover Township, Athens County, Ohio, United States. As of the 2010 census it had a population of 341. Although it is unincorporated, it has a post office, with the ZIP code of 45761. It is located near State Route 13 midway between Chauncey and Jacksonville. Route 13 formerly ran through the community, but a bypass relocated it close by.
Millfield is the home of the largest living white oak tree in the state of Ohio, located on the Ancient Oak Farm owned by the Simpkins family.
The Millfield Mine disaster, the worst mine disaster in Ohio history, occurred at Millfield in 1930.
Coordinates: 39°25′58″N 82°05′49″W / 39.43278°N 82.09694°W