Gaston IV of Foix

Gaston IV (27 November 1422 – 25 or 28 July 1472) was the viscount of Béarn and the count of Foix and Bigorre in France from 1436 to 1472. He also held the viscounties of Marsan, Castelbon, Nébouzan, Villemeur and Lautrec and was, by virtue of the County of Foix, co-prince of Andorra. From 1447, he was also viscount of Narbonne.

Gaston was the son of John I, Count of Foix, and Jeanne I d'Albret.

Gaston married Eleanor of Navarre in 1441. Her parents were King John II and Queen Blanche I of Navarre. At the time, Eleanor appeared to have few prospects: her father was the younger son and brother of kings of Aragon, and she had two older siblings, Charles and Blanche, standing between herself and the throne of Navarre. However, family dissent and death eliminated both her siblings; Eleanor's father usurped the Navarrese crown, to which he added in 1458 the throne of Aragon (his older brother having died without legitimate children). Following the deaths of Charles and Blanche, King John promised the succession to Navarre to Eleanor and Gaston in return for their loyalty to him, which was given.

When Gaston IV died in 1472, his eldest son Gaston, Prince of Viana, had already died, and he was succeeded as count of Foix by the latter's son Francis Phoebus who was only 5 years old, under the regency of his grandmother and Gaston IV's wife Eleanor.