Teilo was a leader of the Celtic Christian church in Wales during the 6th century. (His dates of birth and death are unknown.) He was a contemporary of Saint David, with whom he probably travelled to Jerusalem on pilgrimage. Teilo is believed to have been bishop of St David's. Bones found in St. David's Cathedral during restoration work at the turn of the 21st century were thought to be his, but scientific dating proved otherwise. Like most of the Welsh "saints" of this period, Teilo was a monastic leader, and founded a "llan" or monastic settlement which gave its name to the town of Llandeilo in Carmarthenshire. Several other places bear his name, and he is also believed to have preached or taught in Brittany. He is one of the patron saints of Llandaff Cathedral, and is supposed to have founded the original monastery at Llandaff.