Gilli, also known as Gilla, was an early 11th-century Norse-Gaelic lord. According to Njáls saga, Gilli was a Hebridean jarl, centred at on the island of Coll, who paid tribute to his brother-in-law, Sigurðr 'the Stout', Jarl of Orkney (d. 1014). Historian Barbara E. Crawford suggested that Gilli must have controlled an extensive area in the southern Hebrides. Another saga, Orkneyinga saga, also notes Sigurðr's influence in the Irish Sea region; yet it makes no mention of Gilli. During this period in history, Sigurðr governed the Northern Isles, and is thought to have ruled parts of northern Scotland. Sigurðr is also said to have fought in Ireland, at the Battle of Clontarf in 1014. Recently, Clare Downham, noted that while it is possible that Sigurðr was testing his power in the Hebrides, as the saga literature implies, contemporary sources give little insight on the matter. Crawford noted that the portion of the hoards, found in 'Scandinavian Scotland', which date to the years 975–1025, coincide with the time when Sigurðr is thought to have extended his power into the Hebrides and the aftermath of his defeat at Clontarf.
Gilli's wife is recorded in Njáls saga as Hvarflǫð. This name, according to Donnchadh Ó Corráin, is an Old Norse form of the very rare Irish language name Forbfhlaith. Gilli's own name has also been considered to be at least represented in a Gaelic form. "Gilli" may only the first half of his name. For example, a king of Norway named Haraldr Gilli was born and raised in Ireland; and likely originally bore the name of Giolla Criost, which was afterwards shortened in Norway. In this way, Gilli's full Gaelic name could equate to Gaelic forms of Gillecolum, Gillepatrick, Gillechrist; or any name composed of the Gaelic Giolla (meaning "servant") + [a saint's name].
Njáls saga is a mediaeval Icelandic saga, set during the years 960–1020.
The saga states that Jarl Sigurðr sent one of his bodyguards, Kári, to the Hebrides to collect tribute from Jarl Gilli. Several years later Kári and the sons of Njál, harried Anglesea and the Hebrides. After a successful raid on Kintyre, they went south and harried Wales. They then turned for the Isle of Man where they fought a Manx king called Guðrøðr, killed his son Dungal, and took great spoil. They then travelled to Coll where Gilli greeted them kindly and stayed with him for a while. Gilli then accompanied them back to Orkney to meet Sigurðr. The next spring, Sigurðr gave his sister, Nereiður, to Gilli; and together the newly-weds travelled back to the Hebrides. At Yule, Gilli revisited Orkney on the invitation of his brother-in-law, Sigurðr. After returning to the Hebrides, the next spring, Gilli had a dream in which a man named Herfinnur came from Ireland and sang a song of the death of Brian Boru.
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- Crawford, Barbara E. (1987), Scandinavian Scotland, Scotland in the Early Middle Ages, Leicester University Press, p. 26, ISBN 0-7185-1197-2
- Downham, Clare (2007). Viking Kings of Britain and Ireland: The Dynasty of Ívarr to A.D. 1014. Dunedin Academic Press. p. 196. ISBN 978-1-903765-89-0.
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- Crawford, Barbara E. (1987), Scandinavian Scotland, Scotland in the Early Middle Ages, Leicester University Press, p. 133, ISBN 0-7185-1197-2
- Donnchadh Ó Corráin. "Viking Ireland – Afterthoughts" (pdf). www.ucc.ie. p. 23. Retrieved 28 November 2009.
- Skene, William Forbes (1886). Celtic Scotland: A History of Ancient Alban 3. Edinburgh: David Douglas. pp. 30–31.
- Munch, Peter Andreas (1860). The chronicle of Man and the Sudreys. Brøgger & Christie. p. Notes 44.
- Oram, Richard D. (2000). The Lordship of Galloway (Illustrated ed.). John Donald. p. 53. ISBN 978-0-85976-541-1.
- "Brennu-Njáls saga". www.sagadb.org. Retrieved 29 November 2009.