Corndon Hill is a hill in Powys, Mid Wales, whose summit rises to 513.6 metres (1,685 ft) above sea level. It has a topographic prominence of 203.1 metres (666 ft), so is listed as a Marilyn.

The England–Wales border, sometimes referred to as the Wales–England border or the Anglo-Welsh border, runs for 160 miles (260 km) from the Dee estuary, in the north, to the Severn estuary in the south, separating England and Wales.