Posidonius (Catalan: Possedoni) was the bishop of Urgell in northern Spain between 814 and 823.[1][2][3] He may have become bishop as early 803, the last year when Archbishop Leidrad was still clearly in control of the diocese following the ouster of Bishop Felix for heresy.[4]
Posidonius was not a native of Urgell. Prior to becoming bishop, he was the first Benedictine abbot of Sant Sadurní de Tavèrnoles, appointed by the reformer Benedict of Aniane. A document of 1040 records that he gave some land he owned to the monastery when he became abbot. He procured a diploma from King Louis of Aquitaine (the future Emperor Louis I) permitting the construction of monasteries on fiscal lands. Possibly he was a former member of Louis's court.[4]
Posidonius is recorded as bishop in a donation made by Fredelao, count of Cerdanya and Urgell, in 815 for the benefit of the monasteries of Sant Sadurní and Sant Esteve i Sant Hilari that Fredelao had built in Cerdanya on land he had received from the Emperor Louis.[5] A supposed privilege issued to Posidonius by the Emperor Louis in 835 or 836 is a later forgery.[1] The last authentic reference to Posidonius as bishop is a confirmation of immunity for the monastery of Santa Maria de Gràcia de Senterada issued by Count Matfrid of Orléans at the bishop's request on 21 June 823.[4]