| Petronilla of Aquitaine | |
|---|---|
| Countess of Vermandois | |
| Born | c. 1125 Poitiers |
| Died | c.1151 Saint-Quentin |
| Burial | Crépy-en-Valois |
| Spouse | Ralph I, Count of Vermandois |
| Issue | Elisabeth, Countess of Vermandois Ralph II, Count of Vermandois Eleanor, Countess of Vermandois |
| House | Ramnulfids |
| Father | William X, Duke of Aquitaine |
| Mother | Aénor de Châtellerault |
Petronilla of Aquitaine (c. 1125 – c.1151) was a French noble. She was the second daughter of William X of Aquitaine and Aenor of Châtellerault. She was the elder sister of William Aigret and the younger sister of Eleanor of Aquitaine, who was Queen consort of France, later 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).