Amlaíb (Óláfr Godfridsson) (d. 941), Norse king of Dublin, was son of Gofraid (king 921–34), the last surviving grandson of Ímar (qv); nothing is known of his mother. He married Aldgyth, daughter of an Anglo-Danish jarl, Ormr. If he had any children, they were not very prominent. Amlaíb succeeded to the kingship of Dublin on the death of his father (934), having first come to notice in 933 when he led the Strangford Lough vikings in a raid on Armagh. After taking slaves and plunder he was pursued and defeated by the king of Ailech, Muirchertach na Cochall Craicinn (qv). To solidify his possessions, in 935 Amlaíb led a raid to Lough Ree on the Shannon where he captured a rival Scandinavian leader, Amlaíb Cennchairech (‘scabby head’), leader of the Limerick vikings, and destroyed his ships. Amlaíb established his cousin Haraldr as king of Limerick, thus ensuring that he controlled the vikings of Dublin, Limerick, Waterford, and Strangford Lough. This left him in an excellent position to pursue his ambitions in York. Smyth has stated that this achievement ‘constituted a federation of Scandinavian towns under the rule of Dublin’.
To build up his army, Amlaíb raided Lagore crannóg and Knowth ‘in the same week’ in 935. According to the annals, he then left for Northumbria, returning the following year to plunder Cell Chuilinn (Kilcullen, Co. Kildare), where he captured a thousand prisoners. In 936, the high-king, Donnchad Donn (qv), burned Dublin, but the effect of this on Amlaíb was not too serious: the next year he led a coalition of Norse, Scottish, and Strathclyde Britons against Athelstan, king of Wessex; Amlaíb was also allied to the Danish controller of the vale of York as well as to the Anglo-Danish merchants of the city. But Athelstan, who had once expelled Amlaíb's father Gofraid from York, inflicted a crushing defeat on Amlaíb's coalition at the battle of Brunanburh in Northumbria. The Annals of Ulster record: ‘A great lamentable and horrible battle was cruelly fought between the Saxons and the Norsemen, in which several thousands of Norsemen, who are uncounted, fell, but their king, Amlaíb, escaped with a few followers. A large number of Saxons fell on the other side, but Athelstan, king of the Saxons, enjoyed a great victory.’
Amlaíb took shelter in Strathclyde before returning to Dublin in 938. He started to plunder again to rebuild his men's morale; in this year he plundered Cell Chuilinn, but Donnchad Donn and Muirchertach led a joint Uí Néill raid on Dublin and besieged ‘the foreigners’, ravaging the lands of the Norse from Dublin to ‘Áth Truisten’ (probably on the River Geese, Co. Kildare). Muirchertach was later surprised by the vikings at his palace of Ailech in Inis Éogain and was captured in a daring raid by the Scandinavian fleet; however, he was allowed to ransom himself.
Amlaíb led a second invasion of Northumbria in 939, exploiting the death of Athelstan and the fact that his successor, Edmund, was only 18 years of age. He occupied York, leaving behind as king of Dublin a certain Sitriuc (possibly a junior kinsman), who was captured in 939 by Muirchertach. In conjunction with his ally Archbishop Wulfstan, Amlaíb overran Danish Mercia, besieging the towns of Northampton and Tamworth, and having to fight King Edmund. He captured a very important Mercian lady, Wulfrun, mother of a thegn of the Mercians and of a Northumbrian ealdorman. Mercia was then divided along Watling Street by means of a treaty between Amlaíb and Edmund, leaving Amlaíb in control of York and the five boroughs (Lincoln, Nottingham, Derby, Stamford, and Leicester). The two archbishops of England – Amlaíb's ally Wulfstan, archbishop of York, and Edmund's ally Odo, archbishop of Canterbury – played crucial roles in this arrangement. This made Amlaíb king of Dublin, Northumbria, and Danish Mercia. In 940, he was joined in York by his cousin Amlaíb Cuarán (qv). Amlaíb son of Gofraid died in 941 after leading a raid on Tyninghame in Lothian, and was succeeded as king by Amlaíb Cuarán.