The Synod of Brefi was a church council held at Llanddewi Brefi in Ceredigion, Wales, around 560.
The synod was apparently called in order to condemn the heretical teachings of Pelagius, although this is far from certain. It was an important milestone in the rise of Saint David. The story goes that Saint Paulinus persuaded Saint Dubricius, the senior bishop there, to allow David, a minor abbot, to address the crowd. His words were so eloquent that Dubricius retired in David's favour. One of his first duties was to consecrate Saint Deiniol as Bishop of Bangor. It is also said that the synod was called while Saint Cadoc, Abbot of Llancarfan, was away in Brittany. In disgust, he refused to return for many years.
The Brefi synod was followed by the "Synod of Victory" at Caerleon around 569.