Coordinates: 52°03′17″N 3°09′00″W / 52.05482°N 3.15010°W / 52.05482; -3.15010
Llanigon is a village in Powys, Wales on the edge of the Brecon Beacons National Park, north of the Black Mountains, Wales. The village has approximately 280 inhabitants (2005). The nearest town is Hay-on-Wye, some 1.5 miles (2 km) to the east.
The parish church is dedicated to the mysterious St. Eigon, who may have been a daughter of Caratacus or (more probably) a brother of St. Cynidr of nearby Glasbury. The former interpretation has inspired Barbara Erskine's novel The Warrior's Princess, partly set in Llanigon. The church predates the Norman Conquest, though the current building (parts of which are Norman) is somewhat later.
The manor was formerly known as Llanthomas (or Thomas Church) and was part of the lordship of Hay. Remains of a motte, believed to be 11th or 12th century, survive near the old manor house, which was demolished in the 20th century. In 1522, the manor belonged to Walter Devereux, 1st Viscount Hereford and was said to be the birthplace of William Thomas.