Blacair (Blakkr) (d. 948), king of Dublin, was son of Gofraid and belonged to the Norse-Hebridean dynasty that claimed descent from Ímar (qv) (d. 873). He had at least two brothers, Amlaíb (Óláfr) (qv) (d. 941) and Ragnall. Their father, Gofraid grandson of Ímar, died as king of Dublin and York in 934; his dual kingship was then divided, with Amlaíb succeeding in Dublin and Ragnall in York. With his brother Amlaíb absent in Northumbria from 939, Blacair saw Dublin struggling during the regencies of his cousins Sitriuc and Amlaíb Cuarán (qv). Blacair soon gained a reputation as a military leader; it was he who took action when Dublin was placed under tribute (941) by the powerful king of Ailech, Muirchertach na Cochall Craicinn (qv). To restore something of the city's wealth, Blacair plundered Kildare and Clonmacnoise in 942. The following year, having been left in control of Dublin, he was recognised as king.
The opening of Blacair's reign was certainly auspicious: first, he killed Muirchertach na Cochall Craicinn at Glas Liatháin in Fir Rois (on the Monaghan–Louth border), and took the opportunity to plunder Armagh the next day. Shortly afterwards, he repulsed an assault on Dublin by the recently emerged overking of Leinster, Lorcán son of Fáelán, and slew him. In 944, however, the tables were turned on Blacair when Congalach Cnogba (qv), the Síl nÁedo Sláine candidate for the kingship of Tara, and the new overking of Leinster, Bróen son of Máel-mórda, plundered Dublin and captured much booty. A year later (945), Blacair yielded the kingship of Dublin to his cousin Amlaíb Cuarán. Blacair was killed in 948 in battle with Congalach Cnogba, where, according to the Annals of Ulster, 1,600 of his men were either killed or captured.