Dowlais is a village and community of the county borough of Merthyr Tydfil, in Wales. At the 2001 census it had a population of 6,646. The name is derived from the Welsh du meaning 'black' and glais meaning 'stream'. Dowlais is notable within Wales and Britain for its historic association with ironworking; once employing, through the Dowlais Iron Company, roughly 5,000 people, the works being the largest in the world.