Sennybridge is a village in Powys, mid Wales, situated some 9 miles (14 km) west of Brecon on the A40 trunk road to Llandovery, at the point where the Afon Senni flows into the Usk. The presence of a nearby castle site (NPRN 305090) suggests medieval or earlier origins for a settlement at a river crossing point.
Sennybridge became important in the early nineteenth century with the construction of the terminus depot of the Brecon Forest Tramroad from 1823 until its closure in 1867 (406581). Sennybridge grew further with the establishment of the Neath and Brecon Railway which opened a station in the adjoining village of Defynnog in 1867. In the twentieth century a military camp was established at Sennybridge in 1940 (310059). An extensive training Area (SENTA) lies upon Mynydd Epynt, on land requisitioned for military use, and is still in use today (401496).

David Leighton, RCAHMW, 13 July 2017