Isabella of Brienne (1306–1360) was suo jure Countess of Lecce and Conversano, claimant to the Duchy of Athens and Kingdom of Jerusalem, etc.
Walter V of Brienne hired the Catalan Company, a group of mercenaries founded by Roger de Flor, to fight against the Byzantine successor states of Epirus and Nicaea, but when he tried to cheat and kill them in 1311, they slew him at the Battle of Halmyros and took over the Duchy, making Catalan the official language and replacing the French and Byzantine-derived laws of the Principality of Achaea with the laws of Catalonia, soon making it up as Duchy of Neopatras.
When the duke Gauthier was killed, Isabella's mother Jeanne de Châtillon (died 1354), daughter of count of Porcien, may have tried to hold the Acropolis of Athens against the attacking Catalans, but eventually surrendered it.
Her brother Walter VI of Brienne gradually gained better positions, and by allying with the Angevin kings of Naples, recovered some Italian fiefs.
Isabella's brother Gauthier had left Greece sometime in the 1340s, and her eldest surviving son Sohier of Enghien apparently was resident lord of Argos and Nauplia from c. 1350.
Isabella's fourth son Louis of Enghien, Lord of Conversano, received the (titular) Duchy of Athens in 1381, when his nephew's inheritance was divided.