Llanrhaeadr-ym-Mochnant is a village in Powys, Wales. Until 1974, Llanrhaeadr ym Mochnant was split into two civil parishes, the northern parish being in historic Denbighshire and the southern parish in historic Montgomeryshire. The divide continued between 1974 and 1996, with the former Denbighshire parish being placed in Clwyd and former Montgomeryshire parish in Powys. However, in 1996 both parts of Llanrhaeadr ym Mochnant were united within the county of Powys.
In the 2001 Census it had a population of 1,470, of whom 55% were Welsh-speaking.