Llanfyllin is a market town and community in Powys, Wales. The town population in 2021 was 1,586 and the town's name means church or parish (llan) of St Myllin. The community includes the settlements of Bodfach, Ty Crwyn, Abernaint and several farms.

Powys is a county and preserved county in Wales. It borders Gwynedd, Denbighshire, and Wrexham to the north; the English ceremonial counties of Shropshire and Herefordshire to the east; Monmouthshire, Blaenau Gwent, Merthyr Tydfil, Caerphilly, Rhondda Cynon Taf, and Neath Port Talbot to the south; and Carmarthenshire and Ceredigion to the west. The largest settlement is Newtown, and the administrative centre is Llandrindod Wells.