Killamarsh is a town 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 prevented this, even if Killamarsh has an "0114" dialing code and a Sheffield post code.
Killamarsh was mentioned in the Domesday Book with the name Chinewoldemaresc or Chinewolde meaning "Cynewalds Marsh". There are a number of smaller communities within the town. Norwood, Nethergreen, Westthorpe and Upperthorpe surround the main town centre.