Bugi ab Gwynlliw Filwr (also Hywgi, Bywgi and Beugi) was a Welsh Christian saint in the 6th century. He was reportedly the son of Gwynllyw, a Welsh king, brother of saint Cadoc and the father of Beuno (died 640), abbot and saint. His wife Peren, Beren, or Perferen was the daughter of Lleuddun Luyddog, identified as King Lot of Lothian.