Rainhill is a large village and civil parish within the Metropolitan Borough of St Helens, in Merseyside, England. The population of the civil parish taken at the 2011 census was 10,853.
Historically part of Lancashire, Rainhill was formerly a township within the ecclesiastical parish of Prescot, and hundred of West Derby. Following the Local Government Act 1894, it became part of the Whiston Rural District.
Rainhill is most famous for being the location of a pioneering competition to decide a suitable locomotive design for use on the new Liverpool and Manchester Railway, the world's first inter-city passenger railway which was routed through the village. The Rainhill Trials of 1829 resulted in the selection of Stephenson's Rocket as the world's first "modern" steam locomotive.