Philip I, known as Philip of Savoy (1278 – 25 September 1334) was the lord of Piedmont from 1282 until his death and prince of Achaea between 1301 and 1307. He was the son of Thomas III of Piedmont and Guia of Burgundy. Philip's first marriage was celebrated in Rome on 12 February 1301 to Isabella of Villehardouin, Princess of Achaea. They had three daughters: Mary, Alice and Margaret. By that marriage, he became Prince of Achaea, though he had already been lord of Piedmont by inheritance from his father in 1282. He was, however, an authoritative prince and this put him at odds with the baronage of his realm. He tried to placate the barons of Morea, but was forced to accept a parliament in 1304. The Greek archonts from Skorta revolted in 1302. In 1307, King Charles II of Naples, the suzerain of Achaea, confiscated the principality and gave it to his son, Prince Philip I of Taranto. In 1312, Philip married Catherine de la Tour du Pin (died 1337), daughter of Humbert I of Viennois and had issue:

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