Decatur is an unincorporated community in eastern Byrd Township, Brown County, Ohio, United States.
[2] It is located along State Route 125, an east-west highway.
Decatur was originally called St. Clairsville, and under the latter name was laid out around 1802.
[3] A post office called Decatur has been in operation since 1817.
This Brown County, Ohio state location article is a stub.