The Battle of Aguioncha or Aguiuncias, the culmination of a Galician–Portuguese civil war in the Kingdom of León, was fought at the hill called Aguioncha on the river Salas in the province of Ourense between two aristocratic factions. The leader of the victorious faction was the Portuguese count Gonzalo Menéndez, that of the defeated the Galician count Rodrigo Velázquez.
Rodrigo is usually credited as one of the leaders of the party that supported Sancho I and his son Ramiro III in the wars over the Leonese succession that began in the late 950s and continued into the 980s. The chief rival clan was led by Gonzalo, and supported first Ordoño III and later his son Vermudo II. The absence of Rodrigo from court for a total of six years during the reigns of Sancho I and Ramiro III, and his comparatively frequent recurrence in the diplomas of Ordoño III, does not support the hypothesis that he was a creature of the former, as M. R. García Álvarez believed. The rivalry between the two families had more to do with a dispute between Gonzalo's mother, Mummadomna, abbess of Guimarães, and a relative of Rodrigo's, Guntroda, abbess of Pazóo. Guntroda had appropriated the monastery of Santa Comba, which belonged to a monk name Odoino, who appealed to Mummadomna for support. She sent her sons Gonzalo and Ramiro to force Guntroda to return it volens nolens (willing or not).
The date of the battle is disputed. It may have taken place in 966 or 967, during the regency of Elvira Ramírez. If so, the two count were reconciled by 968. Justo Pérez de Urbel argued that the absence of Rodrigo and Gonzalo from court during the regency of Elvira was evidence that during this period they were de facto independent, but they were in León on 20 September 968 for the confirmation of a noble gift to the abbey of Sobrado. On the other hand, it may have occurred between 970 and 974. Gonzalo fell out with Ramiro III in 968 after the latter refused action against the Vikings then ravaging Galicia and Portugal. The resulting bad blood between the families is alluded to as late as 1 October 982 in a document that reads in part: