Caerphilly (Welsh: Caerffili) is a town in Glamorgan, Wales, located at the bottom of the Rhymney Valley. It is the site of Caerphilly Castle, built between 1268 and 1271, and is the main town in the county borough of Caerphilly.

Caerphilly is a parliamentary constituency centred on the town of Caerphilly in South Wales. It returns one Member of Parliament (MP) to the House of Commons of the Parliament of the United Kingdom, elected by the first past the post voting system.

Caerphilly is a constituency of the National Assembly for Wales. It elects one Assembly Member by the first past the post method of election. Also, however, it is one of eight constituencies in the South Wales East electoral region, which elects four additional members, in addition to eight constituency members, to produce a degree of proportional representation for the region as a whole.