Saint Sebastian is situated in Mercer County, in Marion Township. County Road 716A runs through the community. Saint Sebastian is in the Marion Local school district.
In the late 1840's a catholic church was built by the settlers of the area. In 1853, a one room school house was constructed a short distance east of the church. Eventually, the settlement became known as Saint Sebastian.
Among the early businesses of Saint Sebastian were a blacksmith shop, saloon, implement dealer, cane mill, general store, post office and a shoe cobbler.