La più antica descrizione dettagliata dell’Isola di Avalon nella letteratura arturiana, presente nella Vita Merlini di Goffredo di Monmouth, mostra paralleli testuali con la descrizione dell’isola di Sena, sacra presso i Galli, documentata nel De chorographia di Pomponio Mela (III.48). Questo articolo discute i diversi modi nei quali queste analogie possono essere interpretate e conclude che si tratta presumibilmente di prestiti letterari diretti. Parole chiave: Avalon - Sena - Goffredo di Monmouth - Vita Merlini - mitologia celtica. Avalon is one of the most famous otherworld islands of the European literatures of any period. Right from its fi rst appearance in the works of Geoffrey of Monmouth, who was the fi rst to publish a full account of the biography of King Arthur and a description of the Isle of Avalon, it is one of the most central pivots of the geography of Arthurian tradition: it is the place where Excalibur is forged and where Arthur is brought after the battle of Camlan, and where the king is either healed and awaits a future return or succumbs to his wounds and is buried. In spite of this central role in Arthurian literature and the extensive research that has been conducted on Arthurian narratives, there is still no consensus on the question how “Celtic” the oldest extant description of Avalon in Geoffrey’s Vita Merlini is. While Loomis in his classic (though dated) discussions concluded that Geoffrey’s