Turgesius (died 845) (also called Turgeis, Tuirgeis, Turges, and Thorgest) was a Viking chief active in Ireland who is said to have founded 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 ibn-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. Gerald of Wales, who may have had access to a version of this work, included similar accounts in his Topographia Hibernica. These accounts are not deemed trustworthy.
According to The War of the Irish with the Foreigners, Turgesius was married to Ottar or Ota (thought to be Old Norse Auðr or more likely Odda or another name beginning in Odd-), who took possession of the cathedral at Clonmacnoise and gave audiences seated on the great altar. This appears to be a reference to her being a völva or performing spæ. However, the Arabic account of al Djayani's mission to the Vikings calls the king's wife Nūd.
- The Vikings In Scotland And Ireland In The Ninth Century (Donnchadh Ó Corráin. 1998)
- W.E.D. Allen, The Poet and the Spae-Wife: An Attempt to Reconstruct Al-Ghazal's Embassy to the Vikings Dublin: Figgis, Viking Society for Northern Research, 1960, OCLC 557547145, p. 46.
- Charles Haliday, ed. John Patrick Prendergast, The Scandinavian Kingdom of Dublin, Dublin: Thom, 1882, repr. Shannon, Irish University Press, 1969, ISBN 0-7165-0052-3; see Allen, pp. 58-60 and notes 203, 204, p. 93 (calling him Halliday). The theory was first published by John O'Donovan in 1860, prior to the posthumous publication of Haliday's papers.
- Annals of Ulster, AU 845.8; Barbara E. Crawford, Scandinavian Scotland, Leicester University Press, 1987, ISBN 0-7185-1197-2, p. 49, describes this as "the only historical fact that can be relied upon".
- Annals of the Four Masters, AFM 843.13.
- This is the argument of Allen's book.
- Allen, p. 17.
- For the origins of the Cogad, see Ó Corráin, "Ireland, Wales, Man and the Hebrides", pp. 105–106.
- Peter H. Sawyer, Kings and Vikings: Scandinavia and Europe AD 700-111, repr. London: Routledge, 2000, ISBN 0-415-04590-8, p. 22, quotes Ó Corráin, who describes them as a 'farrago'; Crawford, p. 49; Francis John Byrne, Irish Kings and High Kings, London: Batsford, 1973, OCLC 251894543, p. 267. Dáibhí Ó Cróinín, Early Medieval Ireland, 400-1200, London: Longman, 1995, ISBN 0-582-01566-9, p. 262, follows Liam De Paor in describing the Cogad as "about as good a source of information on the Vikings as 'Star Trek' is for the American space programme". Geoffrey Keating's accounts are derived from Gerald; Ó Cróinín, p. 247.
- Allen, p. 46.
- Allen, p. 47.