Turgesius (died 845) (also called Turgeis, Tuirgeis, Turges, and Thorgest) was a Viking chief active in Ireland who is said to have conquered Dublin. It is not at all clear whether the names in the Irish annals represent the Old Norse Thurgestr or Thorgísl. John O'Donovan and Charles Haliday independently identified him with Ragnar Loðbrók, but the identification is not generally accepted. The sole reliable record of Turgesius is a report of his death in the Annals of Ulster. In 845 he was captured by Máel Sechnaill mac Máele Ruanaid of Clann Cholmáin and drowned in Lough Owel. Less certainly, the Annals of the Four Masters associate Turgesius with attacks on Connacht, Mide and the church at Clonmacnoise in the year before his death. The principal island on Lough Lene is named after him. It is speculated that Yahya bn-Hakam el Bekri al Djayani, called al-Ghazal, was ambassador to this Norse ruler. By the twelfth century, when The War of the Irish with the Foreigners (Cogad Gaedel re Gaillaib) was composed to magnify the achievements of Brian Bóruma, Turgesius had become a major figure.