Saint Charles (also known as Isis) is an unincorporated community in Butler County, in the U.S. state of Ohio.
A post office called Saint Charles was established in 1850, and remained in operation until 1905.[1] The U.S. Geographic Names Information System (GNIS) lists the historical location of the post office at 39.3917°N -84.7431°W.
The community was named for Charles Stewart, an early settler.[2]