Llandyfaelog Tre'r-graig (Anglicisation: Llandefaelog-tre'r-graig ), which is  from Cardiff, is a hamlet in the Felin-fach community of the Breconshire, South Powys area of Wales.  There are several forms of the name, including Llandefaelog Tre'r Graig (a 'Tre'r-graig' is added to distinguish between it and Llandyfaelog in Carmarthenshire), for the same reason sometimes referred to as Llandyfaelog Fach).

The village is named after St Tyfaelog.

The village is located  east of Brecon, on the slopes of the hills between the Brecon Beacons to the west and the Black Mountain to the east.  It lies on the rural road between Talgarth to the north and Llanfihangel Talyllyn to the south.  Other nearby villages include Loughstone.  It is about  northeast of Trefeca, associated with the community of the evangelist of the 18th century Howel Harris.

References

Villages in Powys