Killamarsh is a town and civil parish in North East Derbyshire. It borders South Yorkshire to its north and west. It lies between Halfway and Mosborough to the west, Eckington and Renishaw to the south, Beighton and Sothall to the northwest, Wales to the northeast, Harthill to its east and the Rother Valley Country Park to its north. Over the years, South Yorkshire and Sheffield have tried to merge the town into the ceremonial county, but disagreements have prevented this, despite Killamarsh having an "0114" dialing code and a Sheffield address and postcode.