Arenig Fawr (Welsh for 'great high ground') is a mountain in Snowdonia, North Wales, close to Llyn Celyn reservoir, alongside the A4212 between Trawsfynydd and Bala.

Beneath the mountain is Llyn Arenig Fawr, a reservoir providing drinking water to Bala and the surrounding villages.

The summit, which is also known as Moel yr Eglwys (Welsh for 'Bare hill of the church'), has a trig point and a memorial to eight American aircrew who died when their Flying Fortress bomber B-17F #42-3124 crashed on 4 August 1943.

[4] In The Faerie Queene, an incomplete English epic poem by Sir Edmund Spenser, the home of 'old Timon', Prince Arthur's sage foster-father, "is low in a valley greene, Under the foot of Rauran mossy hore".

[5] Welsh historian Sir John Edward Lloyd wrote that Rauran "comes from Saxton's map of Merionethshire (1578), which places ‘Rarau uaure Hill’ (Yr Aran Fawr) where Arenig should be".