917–924) was the count and tenente of Lantarón and Cerezo on the eastern frontier of the Kingdom of León in 923–24.
[1] There is a document dated 28 March 913 which records that King Vermudo was reigning in León and Fernando Díaz in Lantarón.
The historian Gonzalo Martínez Díez has suggested the date should be corrected to 923 and the king to Ordoño II.
This may have been Fernando Díaz, who was active around the same time in the neighbouring region of Álava, or possibly Fernando Ansúrez I, who was certainly count of Castile at a later date.
[2] In January 918, Fernando Díaz was in the city of León, where he signed a document in the cathedral as Fredinandus Didazi comes ("Fernando, son of Diego, count"), without specifying his county.