Llanddewi Brefi is a village on the banks of the Afon Brefi in Ceredigion, West Wales. It derives the second part of its name from a local legend involving two oxen. The oxen were hauling stone up a steep hill when one of them collapsed and died. The other bellowed nine times, and because its bellow was so loud, the place became known as Llanddewi Brefi (brefi meaning bellow).

The villages connection with the Welsh patron saint led to the first part of the village name. In the 6th century Saint David (Welsh: Dewi Sant), held the Synod of Brefi here and it has borne his name since; "Llan" referring in Welsh place names to a church or holy place.

Legend has it that when the crowd that had gathered to see the saint couldn't hear him, he raised the ground from underneath himself so that he was standing on a small hill. This is the same hill that the village church stands on today. St David's Church dates back to the 12th century, although the site has been a place of worship since the 7th century. In the churchyard stand an interesting collection of Celtic crosses, which are worth visiting themselves.

Llanddewi Brefi might ring a bell with some people, as it appeared as the hometown of Little Britain character Daffyd Thomas, better known as “the only gay in the village”.