Coordinates: 51°44′56″N 3°22′08″W / 51.749°N 3.369°W
Cyfarthfa High School is a comprehensive school, based in Merthyr Tydfil County Borough, Wales, that was established in 1970. Cyfarthfa means "Place of the barking (dog)" in Welsh and the school crest reflects this.its got lessons including French Welsh and re.
The school was formed by the amalgamation of Cyfarthfa Castle Grammar School and Georgetown Secondary Modern School. Cyfarthfa Grammar School, opened in 1913, was based in Cyfarthfa Castle operating as separate boys' and girls' schools. In 1945, they amalgamated, and in accordance with the then government policy the school was redesignated as a Grammar school under the name of Cyfarthfa Castle Grammar School. Georgetown Secondary Modern School was located at Georgetown, Merthyr Tydfil.
Initially, the Upper School was located in the Grammar School premises at Cyfarthfa Castle. The Upper School moved to a new campus in Cae Mari Dwn in 1981.
The new site is based a few miles away from the lower school and provides a range of purpose based facilities. It has a brick built building with a hall and external playing fields. The two storey site includes a dedicated science wing, sports hall, a range of general purpose classrooms, a flood-lit Astroturf.
The original lower school was situated in Georgetown, Merthyr Tydfil. At that site it had two wings plus an annex providing science and metalwork facilities. External portable units provided woodwork and language labs. In 1981 the Lower School relocated to the Cyfarthfa Castle site, vacated by the Upper School.