The Ásbirnings were a powerful family clan in the medieval Icelandic Commonwealth. They dominated Skagafjörður in the 12th and 13th centuries until their last leader died in Haugsnesbardagi in 1246. The Ásbirnings were well-known warriors and politicians. The best known Ásbirning is probably Kolbeinn Tumason, a famous Icelandic poet.
References
Árni Daníel Júlíusson, Jón Ólafur Ísberg, Helgi Skúli Kjartansson Íslenskur sögu atlas: 1. bindi: Frá öndverðu til 18. aldar Almenna bókafélagið, Reykjavík 1989