- (1319-1387) King of Aragon, Valencia, Majorca, Sardinia, Corsica, count of Barcelona and of Roussillon. Reigned from 1336. Had the nickname of 'the Ceremonious'.
- Sent a letter of condolences to Pedro of Portugal on the death of his father, Afonso IV (1357). [Pedro, ch. 3: 1, 50]
- Sustained a war initiated by Pedro of Castile (1356) with the intent of taking revenge on his half-brothers, sons of Leonor Núñez de Guzmán who had taken refuge in Aragon. The King of Castile resented the fact that Pero IV of Aragon refused to hand over his own half-brother Fernando, Marquis of Tortosa, to be executed in Castile for his assistance to the Núñez de Guzmán brothers.
- The Castilian-Aragonese war lasted ten years, from 1356 to 1366.
Pere IV