Catherine II of Valois (1303 – 1346) was Titular Empress of Constantinople from 1308 to her death, Princess regent of Achaea from 1332 to 1341, and Governor of Cephalonia from 1341 to her death.
Catherine II was a younger half-sister of (among others) Philip VI of France, Jeanne of Valois and Charles II of Alençon.
Her mother was Titular Empress of the Latin Empire of Constantinople. But the city had been captured by the Empire of Nicaea since 1261. Catherine succeeded her mother as the Titular Empress in 1308. She was still a child and remained in the custody of her father, who managed her claims to the empire until his death in 1325.
In 1313, Catherine married Philip I of Taranto, King of Albania and Prince of Achaea. She associated her husband as titular emperor (Philip II) and retained the claim to the empire after his death on December 23, 1332. Robert was his eldest surviving son and succeeded him as Prince of Taranto. In 1333 he received the principality of Achaea by agreement with his uncle John of Gravina. However the thirteen-year-old boy was deemed too young to reign alone and his mother became his co-ruler for the rest of her life.
In 1339 she arrived in Achaea and took an active part in its government. She gave refuge to Nikephoros II Orsini of Epirus and supported him in his attempt to assert himself in his land against the Byzantine Emperor Andronikos III Palaiologos. Her presence in Achaea was no longer needed by the time Robert reached adulthood in 1341. She became Governor of Cephalonia and spent the last five years of her life in this responsibility.