Juan Fernández de Heredia

Juan Fernández de Heredia (in Aragonese Johan Ferrández d'Heredia, pronounced IPA: [ˈtʃwan feˈrand̪eθ deˈɾedʝa] (c. 1310 – 1396) was the Grand Master of the Knights Hospitaller from 24 September 1377 to his death. His tenure was occupied by the "affair of Achaea." He was also a great patron of the translation and composition of historiographical works in the Aragonese language and a counsellor to two Kings of Aragon.

Heredia was born in Munebrega, Kingdom of Aragon. As a knight of the Hospitaller order (from 1328), Heredia was the commander of the castles of Villel, Aliaga, and Alfambra. He was originally patronised by Peter IV of Aragon and Pope Innocent VI. Through the aid of the latter, he was appointed to govern the grand priories of the kingdoms of Castile and León, and of the abbey of Saint-Gilles in southern France, the richest priory of the order. He supported Peter IV against the Union of Aragon and fought on his side in the successful Battle of Epila (1348).

In 1346, with the king of Aragon's support, he gained the castellany of Amposta (which was the priory of Aragon). Heredia made himself and his family (and illegitimate children) enormously wealthy at the expense of the order. His power and influence was greatly circumscribed by the Grand Master Raymond Berengar, but in 1371 he entered the favour of Pope Urban V and was elevated as the master's lieutenant in Western Europe.

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