John Kavanagh (born 1946, Dublin, Ireland) is an Irish character actor who was a member of the Abbey Theatre company for ten years (1967–1977) before going freelance. He has worked in over 20 films and numerous TV series since 1970. His film credits include Braveheart (1995), The Butcher Boy (1997), Dancing at Lughnasa (1998), Florence Foster Jenkins (2016), and The Last Duel (2021). On television he is best known for playing The Seer / Pope Leo IV in Vikings (2013–2020) and Vikings: Valhalla (2022–2024), and Cardinal Lorenzo Campeggio in The Tudors (2007–2008). He received a Drama Desk Award nomination (1989) for Juno and the Paycock. He is also a singer, having played the lead in the Irish stage production of Jacques Brel Is Alive and Well and Living in Paris in the 1970s. No other personal details are publicly confirmed.