The Tryweryn flooding or Tryweryn drowning , refers to the flooding of the rural community of Capel Celyn to the north west of Bala in Gwynedd, Wales, in the Afon Tryweryn valley. The village and other parts of the valley were flooded in 1965 to create Llyn Celyn reservoir, in order to supply Liverpool and Wirral with water for industry.

Llyn Celyn is a reservoir constructed between 1960 and 1965 including the highly controversial Tryweryn flooding in the valley of the River Tryweryn in Gwynedd, Wales. This included the forcible removal of the Capel Celyn village residents despite protest and opposition of Welsh MPs.