Llanddewi Brefi (Welsh pronunciation: [ɬanˈðɛwi ˈbrɛvi]) is a village, parish and community of approximately 500 people in Ceredigion, Wales.

Today, it is one of the largest parishes in Wales and lies 7 miles (11 km) north-east of Lampeter between Tregaron and Llanfair Clydogau.

[5] The name is subject to a number of folk tales which derives it from an old legend that two oxen (sometimes the "Ychain Bannog" of Hu Gadarn in Welsh mythology) were hauling stone for the construction of the church.

Romans activity in the area is evidenced by the construction of a square auxiliary fort around AD 73 -77, close to a crossing point of the river for which it was named.

Despite this short occupation a settlement of around a thousand civilians is thought to have developed, as evidenced by the extensive archeological evidence and the presence of a Thermae (Roman bathhouse).

Two of five inscribed stones found in the area indicate that the fort's garrison included soldiers from the Cohors II Astrium, a military unit from Asturias, Spain.

[14] In the eleventh and twelfth centuries the area was the scene of much fighting both against the invading Normans and between the established Kingdom of Powys and Deheubarth.

The Norman Bishop of St Davids also established an ecclesiastical college in the village in honour of their patron saint.