Caereinion Fechan was a community in Powys, Wales, and the historic county of Montgomeryshire.
Originally it was a township in the parish of Mallwyd, comprising a small area of Montgomeryshire next to the border with Merionethshire, to the south-west of Aberangell. Much of the area was in the Dyfi Forest.
It was established as a civil parish in 1894 from the part of Mallwyd parish which was in Montgomeryshire. It was included in Machynlleth Rural District. In 1974 it became a community and on 1 April 1987 it was abolished. It is now part of the community of Glantwymyn.
