Ysgol Gyfun Rhydywaun is a Welsh-medium comprehensive school in the Cynon Valley in the village of Penywaun, Rhondda Cynon Taf, Wales, to the northwest of the town of Aberdare.

The school was established on 1 September 1995 to deal with the increasing numbers of students attending five local Welsh-medium primary schools, who previously had to travel to secondary school in Pontypridd. It provides a Welsh-medium education for pupils from the Cynon Valley and from neighbouring Merthyr Tydfil County Borough, where there is no Welsh-medium secondary school.

There are three houses, Cynon, Dâr and Taf, named after the local rivers, Cynon, Dare and Taff.

• Andrew Coombs, Welsh rugby international
• Nathan Craze, British ice hockey international
• Thomas Young, Welsh rugby international
• Steffan Jones, Track and Field Athlete, Student at Harvard University

• Official website