Casstown is a village in Miami County, Ohio, United States. The population was 322 at the 2000 census. It is part of the Dayton Metropolitan Statistical Area.
Casstown is located at 40°3′9″N 84°7′39″W / 40.0525°N 84.1275°W / 40.0525; -84.1275 (40.052583, -84.127577).
According to the United States Census Bureau, the village has a total area of 0.1 square miles (0.3 km²), all of it land.