Tretower (Welsh: Tretwr) is a hamlet in the community of Llanfihangel Cwmdu with Bwlch and Cathedine in the southern part of the county of Powys in Wales. It lies on the A479 road within the Brecon Beacons National Park at the foot of the Black Mountains just off the Usk Valley. Tretower is frequented by tourists visiting the impressive Tretower Court and the nearby ruins of Tretower Castle, both of which are now managed by Cadw.