The Metropolitan Borough of Calderdale is a metropolitan borough of West Yorkshire, England. It takes its name from the River Calder, whose upper part flows through the borough. Several small valleys contain tributaries of the River Calder. The population at the 2011 Census was 203,826.

Calderdale covers part of the South Pennines and is the southernmost of the Yorkshire Dales, though it is not part of the Yorkshire Dales National Park. The borough was formed by the merger of six former local government districts, spanning, from east to west, the towns of Brighouse, Elland, Halifax, Sowerby Bridge, Hebden Bridge and Todmorden. Mytholmroyd is now part of Hebden Bridge, forming Hebden Royd.

Halifax is the main commercial, cultural and administrative centre of the borough, with numerous high street chain stores, markets, central library, borough council offices, public transport hub, central police station and the further and higher education college, as well as other major local organisations. Calderdale is served by Calderdale Council, Calderdale's admin headquarters is in Halifax, with some council organisations based in Hebden Bridge.

The Roman settlement of Cambodunum was probably located within Calderdale. A Roman fort has been excavated in Slack but its identity is not yet certain.

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