Ysgol Dyffryn Ogwen ("Ogwen Valley School") is a school in Bethesda in the Ogwen Valley in Gwynedd, North Wales, with around 400 pupils. Some of the buildings date from 1895 when a County School (grammar school) was established here, but the present comprehensive school dates from 1951. An extension to the school was opened by Professor Sir Idris Foster. The motto of the school is "Bydded goleuni" ("Let there be light", Gen. 1.3)