Elfodd, Elvodug or Elfoddw (Latin: Elbodus or Elbodius; died 809) was a Welsh bishop. He induced the Welsh church to accept the Roman computus for determining the date of Easter endorsed elsewhere in Britain at the Synod of Whitby in 664. This was after centuries of continuing the practice they had taught to the Irish.
Elfodd appears to have been associated with the monastery at Holyhead on Anglesey as a young man and must have still been comparatively young when in 768 he persuaded the Welsh church to come into line with Rome as regards the method of calculating the date of Easter. The annals Brut y Tywysogion state: "Eight years after that  Easter was moved for the Britons, and Elbodius the servant of God moved it".
Elfodd's death is recorded under the year 809. Brut y Tywysogion describes him as "archbishop of Gwynedd", making him bishop of Bangor. Nennius, who says in the History of the Britons that he was a pupil of Elfodd's, describes him as a "most holy bishop" and reveals that Elfodd studied the works of Bede. One later source states that he was consecrated as a bishop in 755, but may not be reliable.
- II. The Apology Of Nennius. “Here begins the apology of Nennius, the historiographer of the Britons, of the race of Britons. 3. I, Nennius, disciple of St. Elbotus” Translated by J. A. Giles, an asterisk is attached to the name “St Elbotus” stating “Or Elvod, bishop of Bangor, 755 AD, who first adopted in the Cambrian Church, the new(Roman) cycle for regulating Easter
- John Edward Lloyd A history of Wales from the earliest times to the Edwardian conquest (Longmans, Green & Co.)
- Thomas Jones, ed. Brut y Tywysogion: Peniarth MS. 20 version (Cardiff: University of Wales Press, 1952)