Petronilla of Aquitaine (c. 1125 – 1193) was the daughter of William X of Aquitaine and Aenor of Châtellerault She was the sister of Eleanor of Aquitaine, who was Queen consort of England. She is variously called Alix (or Aelith in Occitan) and Petronilla; she typically went by Alix after her marriage, while Petronilla seems to have been her childhood name (she is referred to as such in her father's will).