Ansur, Assur, or Asur Fernández (died 947/50) was a powerful Castilian nobleman and military leader in the Kingdom of León during the reign of Ramiro II.
The earliest reference to Ansur is found in a document dated 4 March 921, wherein he is named with his parents Fernando Ansúrez and Muniadonna in a donation in the vicinity of Burgos to San Pedro de Cardeña.
In July 941 Ramiro associated the counts of the Banu Ansúrez and Gómez families as well as Fernán González and Sancho Garcés II of Pamplona with him in a peace treaty signed with the Caliphate of Córdoba.
By this act Ansur, his wife Guntroda,[5] and their children—Fernando, Oveco, Muño, Nuño, Gutierre, Gonzalo, and Teresa[6]—donated the village of Fuente Adrada near Sacramenia to the monastery of San Pedro de Cardeña.
[7] After Ramiro deposed Fernán González in Castile, he appointed his own son, the future Sancho I, as count with Ansur acting as his "regent".