Gaston I of Foix or Gaston VIII of Foix-Béarn (1287 – Maubuisson, 13 December 1315) was the 9th Count of Foix, the 22nd Viscount of Béarn and Co-Prince of Andorra.
He was a son of Roger-Bernard III, Count of Foix and Margaret of Montcada, the eldest daughter and heiress of Gaston VII of Béarn. He succeeded his father in 1302 as Count Gaston I of Foix and Viscount Gaston VIII of Béarn, first under the regency of his mother.
He was probably present at the Battle of the Golden Spurs in 1302, and fought again for the King of France against the Flemish at the Battle of Mons-en-Pévèle in 1304. When the cities of his County of Foix rebelled against the Royal tax collectors, because they raised the taxes to finance the expensive war against Flanders, Gaston supported his cities. For this, the County was confiscated for a while by the Senechal of Carcassonne.
In 1308, he started a war against the Count of Armagnac, against the orders of the King, who had forbidden intra-French warfare. Gaston was taken prisoner and locked up in the Châtelet. He was only released after paying a ransom of 36,000 pond. He also had armed conflicts with his uncle James II of Majorca and even with his own mother, who firmly ruled Foix during his many absences.
In 1310, he inherited the Viscounty of Marsan from his aunt Constance of Moncada. When another uncle, Ermengol X, Count of Urgell, died without a male heir, Gaston claimed the County of Urgell, but was no match against King Alfonso IV of Aragon, who incorporated Urgell into the Crown of Aragon.