- (1355-1435) First Lord of Baena and Marshal of Castile.
- Son of Gonzálo Fernández de Córdoba y Biedma and María García Carrillo.
- Chief-Justice (alguazil-mor) of Cordoba.
- Pedro of Castile ordered Martín López de Córdoba to kill him as punishment for welcoming Enrique of Trastámara when he entered Castile to claim the throne, but he refused, and so Diego Fernández escaped with his life. (Fernando, ch.13:22)
- Participated in the siege of Lisbon (1384), and the battles of Aljubarrota and Valverde (1385).
- In 1393 he was sent to Portugal as a plenipotentiary ambassador to negotiate a fifteen-year truce. A legitimate son of his is one of the hostages handed over to Don Álvaro Gonçalves, Prior of the Order of the Hospitallers, as one of the hostages to guaranty the treaty. [João2, ch. 150]
Diego Fernandez