St. Sebastian is situated in Mercer County, in Marion Township. County Road 716A runs through the community. St. Sebastian is in the Marion Local school district.

In the late 1840's a Catholic Church was built. In 1853, a one room school house was constructed a short distance east of the church.

St. Sebastian had a blacksmith shop, saloon, implement dealer, cane mill, general store, post office and a shoe cobbler.