Ysgol Gyfun Cwm Rhymni is a vibrant, pioneering and successful 11-18 Welsh-medium comprehensive school serving the County Borough of Caerphilly. The school is located on two sites: Gelli Haf near Blackwood, and Gwyndy in the heart of Caerphilly itself.

Every subject apart from English is taught through the medium of Welsh. The school was rated as 'Good' in all Key Questions by Estyn in the most recent inspection. They also noted that both the learning experiences and learning environment provided by the school are 'Excellent'. The school provides a wide range of courses in the sixth form, including those at A/AS level and vocational courses.