Fernando Díaz de Haro was a Spanish noble of the House of Haro. He was the second born son of Diego López V de Haro, the Lord of Biscay, and his wife, the infanta Violante de Castilla y Aragón, daughter of Alfonso X of Castile. Fernando became lord of Orduña and Balmaseda in 1322, after the death of his brother, Lope Díaz IV de Haro who died without leaving any descendants.