Castleside is a village in County Durham, in England. It is situated a short distance to the south-west of Consett. The village centre is located on the main A68 road which runs between Edinburgh and Darlington and the village crossroads allow easy access to Consett, the North Pennines and Stanhope. To the northeast lies another small village called Moorside.
The parish church, dedicated to St John, was designed by Ewan Christian and is a reproduction of a church he had seen and admired while on holiday in Switzerland. The church was consecrated on 7 March 1867.