Guy of Hauteville (Italian Guido d'Altavilla; died 5 July 1108) was an Italo-Norman soldier and diplomat who for a time served the Byzantine Empire.
[1] After his father's death, Guy entered the service of his erstwhile enemy, Emperor Alexios I Komnenos.
In August 1096, he helped negotiate between the Alexios and the leaders of the First Crusade, even serving as a hostage for the emperor's good faith during the dealings with Godfrey of Bouillon.
Guy was with the Byzantine army campaigning in Asia Minor when, at Philomelium around 20 June 1098, it was met by the nominal leader of the Crusade, Stephen, Count of Blois, who reported that the siege of Antioch was going very badly.
He returned to Italy shortly after and died there on 5 July 1108, as recorded in the necrology of the Cathedral of San Matteo in Salerno.