Garneddwen (also known as Garnedd-Wen; English: white cairn) is a hamlet in the south of the county of Gwynedd, Wales.

It lies in the historic county of Merionethshire/Sir Feirionnydd, in the valley of the Afon Dulas.

It consists primarily of a single row of terraced houses, built for the workers at Aberllefenni Slate Quarry.

Nearby is Fronwen, built as a family home by the quarry manager Robert Hughes (1813–1882) and his wife Jane née Deakin (1822–1906).

The hamlet gives its name to the Garnedd-Wen Formation, a thick rock strata that runs from Tywyn to Dinas Mawddwy and was first identified close by the settlement.