Ystradyfodwg or Ystrad Dyfodwg (Vale of Tyfodwg) was an ancient upland parish in Glamorgan, Wales. It is believed to have been named after Dyfodwg (or Tyfodwg), a 6th-century Saint or chieftain. The parish included most of the area, which would later be known as Rhondda, and was named after the parish rivers, Rhondda Fawr and Rhondda Fach.
History of Ystradyfodwg.
The small village of Ystradyfodwg was centred on its parish church, at the site now occupied by the church of St John the Baptist in Ton Pentre. Prior to the industrial revolution, Ton Pentre (then just called Ton) was a hamlet a short distance to the west of Ystradyfodwg, but as Ton grew, it absorbed the older village. A railway station opened at Ystradyfodwg in 1861 on the Taff Vale Railway's Rhondda branch line, with the station initially called Ystrad. It was renamed Ystrad Rhondda in 1930 and renamed Ton Pentre in 1986 when a new Ystrad Rhondda railway station also opened about a mile further down the line to the east.
A local government district, governed by a local board, was established in 1877, covering most of the parish of Ystradyfodwg but excluding the Rhigos area. The district was enlarged in 1879 to cover parts of the neighbouring parishes of Llanwonno and Llantrisant.
The local government district became the Ystradyfodwg Urban District in 1894 when the parish boundaries were also adjusted to match the urban district. In 1897, the Ystradyfodwg Urban District Council formally changed the name of the parish and urban district from Ystradyfodwg to Rhondda.