A literal English translation of the name Pontarddulais is "Bridge on the Dulais", with Dulais meaning "black stream", probably due to its journey through coal measures. The earlier name of Pontaberdulais is in reference to a dismantled 14th century road bridge over the Loughor River (Afon Llwchwr) which formed part of the main highway between Swansea and Carmarthen. The Bridge was so named because of its position upstream of the mouth of the Dulais stream, and not as many believe, because of it spanning the Dulais stream. The Pontaberdulais bridge spanned the River Loughor. This bridge was also known as "Y Bont Fawr". The village that developed around this bridge took the shortened form of Pontardulais as its name, also written as Pontarddulais because of the assumption that the bridge was "over Dulais". The bridge also gave the town its nickname "Y Bont" ("The Bont").
Most of the town lies within the Parish of Llandeilo Tal-y Bont (apart from the small section west of the bridge that lies in LLanedi Parish). LLandeilo Tal-y Bont (the Church of St Teilo at the end of the bridge) also contains a bridge in its name, but this is not to be confused with the Pontaberdulais bridge. The church bridge was located near to the old church on the earlier Roman road that crossed the river Loughor near Hendy. The medieval church was carefully reconstructed stone by stone and now stands proudly in The Museum of Welsh Life in St Fagan's Cardiff.
The Council wishes to thank Mr Deric John for supplying the above place name history.