The Dowlais Ironworks was a major ironworks and steelworks located at Dowlais near Merthyr Tydfil, in Wales. Founded in the 18th century, it operated until the end of the 20th, at one time in the 19th century being the largest steel producer in the UK. Dowlais Ironworks were the first business to license the Bessemer process, using it to produce steel in 1865.
Dowlais Ironworks was one of the four principal ironworks in Merthyr. The other three were Cyfarthfa, Plymouth, and Penydarren Ironworks.
The works was founded as a partnership on 19 September 1759. There were nine original partners including Thomas Lewis and Isaac Wilkinson. The purpose of the partnership was the:
... art misterry, and business of an iron master and iron manufacturer, and for that purpose to build a certain ffurnace or ffurnaces for smelting of iron ore or mine or stone into pig iron in the parish of Merthyr Tidvil for a term of 99 years, and that with the joint stock of £4,000 which the said partners hav agreed to bring in, advance and deliver in and before the first day of January AD 1760.
Lewis brought to the partnership a complex system of leases that allowed the erection of a furnace and the right to mine iron ore, coal and limestone at Dowlais, Pantyrwayn and Tor-y-Fan. Wilkinson brought in his patented machine for blowing furnaces. The other partners brought in capital and various other leases and mineral rights.