Born in 1331 - Orthez, 1391.
Son of Gaston II, he owes his nickname to a somewhat pedantic pun between Foix and the doublet of Apollo
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Like almost all those of his house, but with consummate art, he leads an incessant game of seesaw between the sovereigns of France and England. At first loyal to Philippe VI, he refuses the homage of Béarn to Jean II who has sympathy for the Count of Armagnac. Relying on the Great Companies, he waged war against Jean Il, d'Armagnac whom he defeated and took prisoner at Launac in 1362. If he demanded a fantastic ransom (300,000 florins) and obtained it, the promise of good peace that the counts of Foix and Armagnac swear to each other will have no more effect than those that preceded it. Thanks to the ransom money, Gaston III holds a sumptuous court in Orthez which will impress Froissart. In 1377, he became useful to Charles V who sought to attach him to himself by appointing him governor of Languedoc in 1380. The advent of Charles VI under guardianship led to the withdrawal of this charge in favor of the Duke (the Berry. long disorders on the borders of Languedoc and Gascony. The execrable administration of the duke leads the new king finally emancipated to return to Gaston his province. In 1390, before dying, this one designates his sovereign as universal legatee of his domains .
Passionate about hunting, he wrote an erudite and rather painful treatise on this subject, Le Miroir de Fébus.
Brave, friend of the arts, Gaston Phébus seems to have acted, not only as a wise lord, but, at least at the end of his life, in long-sighted politics, aware of the benefits that French unity could bring to the Pyrenees. Unfortunately for his fame and those close to him, he was, despite his mystical repentance, prone to debauchery and of a rare rapacity, even among the counts of Foix. The violence of his character bordered on madness. It is generally accepted that he killed with his own hands, without wanting to kill, his only legitimate son, Gaston, whom he had very lightly suspected of having wanted to poison him (1382).
On the death of Gaston Phébus, Charles VI ceded his rights to Mathieu de Castelbon.