Gyfarllwyd Falls is a waterfall on the Afon Rheidol in mid Wales, situated within a steep-sided gorge clothed in ancient Welsh oak woodland near Devil's Bridge in the Cambrian Mountains.

The falls lie a short way north of the confluence of the Afon Tuen and the Afon Rheidol, and can be viewed through the trees from the Devil's Bridge site, where a free viewing telescope is provided for a closer look.

The surrounding ravine and woodland form part of a nationally significant natural environment.

A 2025 bryophyte survey recorded the liverwort Radula holtii — new to Wales — on riverside rocks in the shaded ravine immediately above the falls, underlining the ecological importance of this stretch of the river.