The name Cwmtwrch derives from the "Twrch Trwyth", a mythicalwild boar of King Arthur's legends and the ancient Welsh folkloretales of the Mabinogion in early Welsh literature. The legend relates to one of Arthur's tasks: to rid the western Brecon Beacons of the pack of wild boars that were terrorizing the people. Arthur chased the boars from Dyfed eastward towards Powys. On the Black Mountain, he picked up a large stone and cast it towards the wild animals, striking dead the leader of the pack on the edge of a valley near Craig-y-Fran Gorge. The big boar's body rolled down the valley and into the river which is now the Afon Twrch. The big stone is still on the mountain. Cwmtwrch has been split into two parts, Upper Cwmtwrch and Lower Cwmtwrch, due to the traversing of the now defunct railway line and road at two points requiring an upper and lower gate. Nearby is the town of Ystradgynlais and villages of Ystradowen, Rhiwfawr and Ystalyfera.
Governance
Cwm-twrch is the name of the electoral ward which covers the western quarter of the Ystradgynlais community and includes Cwmtwrch Isaf and Cwmtwrch Uchaf to the south. In 2004 a slice of the neighbouring Neath Port Talbot ward of Ystalyfera, bordering Cwmtwrch Isaf, was transferred to the Cwm-twrch ward. The ward elects one county councillor to Powys County Council. A Cwmtwrch & Gurnos ward is represented by up to four town councillors on Ystradgynlais Town Council.
Sport
Cwmtwrch is home to the rugby union team Cwmtwrch RFC a Welsh Rugby Union affiliated club with over a hundred years of history. A resident is Clive Rowlands, former Wales national rugby union team captain, who also managed both the national team and the British Lions. The village football team, Cwmtwrch Wanderers AFC, is long established and successful having won the Neath Premier division on 16 occasions. They have also won 15 cups to make them the most successful team in the league's history. Golf is played at Palleg Golf Club which is located in Lower Cwmtwrch. A mountain course, it was extended to eighteen holes through lottery funding.
