Coordinates: 51°43′16″N 3°27′23″W / 51.721187°N 3.456308°W / 51.721187; -3.456308
Trecynon is a village near Aberdare situated in the Cynon Valley, in Rhondda Cynon Taf, Wales. It dates from the early nineteenth century and its developed as a result of the opening of the Aberdare Ironworks at Llwydcoed in 1800.
The settlement was originally known as Heol-y-Felin (translated as Mill Street) due its location on the road to Llwydcoed Mill. This name was still in use in 1855 when Heolyfelin Chapel was established. The name Trecynon was adopted around 1860 after a competition was held at a local eisteddfod competition to decide upon a name for the village.
In 1811, the Robertstown Tramway Bridge, was built over the river Cynon, linking Heolyfelin and Robertstown. It is the oldest of its kind in the world.
Until 1800 there was only one house at Heol-y-Felin, next to Hen-Dy-Cwrdd Unitarian Chapel, built in 1751. As the iron industry attracted migrants to the Aberdare District there was an increased demand for housing, and, as a result Heol-y-Felin began to grow. Many of the earliest houses in were built along the main road from Aberdare to Hirwaun.