Petronilla, whose name is also spelled Petronila or Petronella, was Queen of Aragon (1137–1164) from the abdication of her father, Ramiro II, in 1137 until her own abdication in 1164. After her abdication she acted as regent during the minority of her son Alfonso II of Aragon (1164–1173). She was the last ruling member of the Jiménez dynasty in Aragon, and by marriage brought the throne to the House of Barcelona.

Ramiro II, called the Monk, was a member of the House of Jiménez who became king of Aragon in 1134. Although a monk, he was elected by the Aragonese nobility to succeed his childless brother Alfonso the Battler. He then had a daughter, Petronilla, whom he had marry Count Ramon Berenguer IV of Barcelona, unifying Aragon and Barcelona into the Crown of Aragon. He withdrew to a monastery in 1137, leaving authority to Ramon Berenguer but keeping the royal title until his death.