Penydarren Ironworks was the fourth of the great ironworks established at Merthyr Tydfil in South Wales.
Built in 1784 by the brothers Samuel Homfray, Jeremiah Homfray, and Thomas Homfray, all sons of Francis Homfray of Stourbridge. Their father, Francis, for a time managed a nail warehouse there for Ambrose Crowley. Most of the family were involved in trade as ironmasters or ironmongers (in this context meaning a manufacturer of iron goods). Samuel built Penydarren House on the opposite bank of the River Taf, as a home for the family locally.
Because the owners of the Cyfarthfa Ironworks dominated the management of Glamorganshire Canal, the other Merthyr Tydfil ironworks built a tramroad to Abercynon, bypassing the upper sections of the canal. This "Penydarren Tramroad" (more correctly, the Merthyr Tramroad) was used for a trial of the first railway steam locomotive, built by Richard Trevithick. This successfully hauled wagons but was so heavy that it broke many rails. The engine was then used for other purposes as a stationary engine.
Coordinates: 51°45′29″N 3°22′14″W / 51.7581°N 3.3705°W / 51.7581; -3.3705
Penydarren (Welsh: Pen-y-darren) is a community in Merthyr Tydfil County Borough in Wales.
The area is most notable as being the site of a 1st-century Roman fort, and during the Industrial Revolution it housed Penydarren Ironworks the third largest of the great Merthyr works. Penydarren was also used by Richard Trevithick as the location for his experiments into steam locomotion. The community and ward has a population of 5,253, increasing to 5,419 at the 2011 Census.
Penydarren Park, the site of the Roman fort and the football ground, is today outside the community boundary.
Being located on a spur of land 700 feet (210 m) above sea level, just southwest of the River Taff, made Pen-y-Darren an ideal location to build an occupation outpost fort for the Romans in AD75, during the governorship of Sextus Julius Frontinus. It was during this period that he subdued the Silures and other hostile tribes of Wales by establishing a new base at Caerleon or Isca Augusta for Legio II Augusta, and this was one of a network of smaller forts fifteen to twenty kilometres apart for his auxiliary units.