Ystrad Mynach is a town located in the Rhymney Valley within the Caerphilly County Borough of Wales, situated in the ancient county of Glamorgan. It is positioned approximately 5 miles (8.0 km) north of the town of Caerphilly and lies within the community of Gelligaer.
The urban area had a recorded population of 19,204 in 2011. Historically, the valley was a rural and farmed region prior to the Industrial Revolution and the subsequent development of coal mining in the South Wales Coalfield.