Llanfihangel-yng-Ngwynfa () is a former parish in Montgomeryshire, now forming a major part of the community of Llanfihangel in Powys, which covers an area of 5,366 hectares (20.72 sq mi). Its Community Council extends to take in Dolanog and Llwydiarth, having approximately 413 registered voters (as at 2012). The parish originally consisted of the following townships: Cefncleisiog, Cydwnfa, Dolwar, Fachwen, Farchwell, Fynnonarthwr, Garthucha, Halfen, Llaethbwlch, Llwydiarth, Nanty-Candy, and Rhiewlas. Dolanog seceded from Llanfihangel in 1856.
Poet and hymnwriter Ann Griffiths (1776–1805) was born in, and is buried, in this place.
