Penydarren Ironworks (Merthyr Tydfil)

The Penydarren Ironworks was a Welsh ironworks founded by Samuel Homfray in 1784 in Merthyr Tydfil, South Wales. The works was an early integrated puddling and rolling iron mill operating to the new processes pioneered by Henry Cort. It was at Penydarren that ironmaster Homfray commissioned Richard Trevithick to build the world's first known railway locomotive, the Penydarren locomotive of 1804, for the works' Merthyr Tramroad to the Glamorganshire Canal.

The locomotive was built in the works' own engineering shops in 1803–1804 and made its famous trial run on 21 February 1804, hauling 10 tons of iron and 70 men. The Penydarren works continued in iron production until 1859 and is commemorated by an exhibition at Cyfarthfa Castle Museum in Merthyr.