Walter of Oxford (died 1151) (Latin: Valterus Calenius[1]) was a cleric and writer. He served as archdeacon of Oxford in the 12th century. Walter was a friend of Geoffrey of Monmouth, who claimed he got his chief source for the Historia Regum Britanniae from him.
In the dedication to his Historia Regum Britanniae, Geoffrey claims that while writing the book he had struggled to find material on the early Kings of the Britons. This problem had been solved when Walter gave him a "very ancient book" written in britannicus sermo (The "British" tongue, i.e. Brittonic, Welsh, or Breton). Geoffrey claims that his Historia is a faithful translation of that book into Latin.[2] However, few modern scholars believe this to be true.[3]