- King of León and Castile 1334-1369, became king in 1350, aged fifteen years and seven months. Son of Alfonso XI of Castile and Maria of Portugal, daughter of Alfonso IV of Portugal. [Pedro, ch. 17: 15]
- Pedro earned the nickname of 'the Cruel' for many acts of cruelty against those he considered his enemies, especially Leonor de Guzmán, his father's lover, whom he killed to revenge his mother's unhappiness.
- King Pedro was killed by Leonor de Guzmán's son and his own half-brother, Enrique de Trastámara, in Montiel, 1369.
- Instigator of the Battle of Barcelona, integrated in the war waged against Pedro IV of Aragon. [Pedro, ch.24]
- Pedro of Castile had Muhammed VI, the Red Emir of Granada killed and sent his head to his rival, Muhammed V. [Pedro, ch. 33: 73-83]
- Pedro sent his daughters to Portugal to make an alliance with his uncle, Pedro King of Portugal, and in order to keep them safe from his half-brother Enrique's invasion of Castile. [Pedro, ch. 36: 7-18, 34-36]
- Pedro also ran away to Portugal, wanting to carry as much of his treasure as he could, but the galley where it was to be carried was taken over and much of the treasure ended up in Enrique de Trastámara's hands. To make matters worse, his uncle Pedro of Portugal found a good excuse not to assist him. [Pedro, ch. 36: 39-44; ch. 37]
- Pedro of Castile went to Bayonne, accepting the Prince of Wales's offer of military assistance against Enrique of Trastámara, who at the time had already been proclaimed king and held most of Castile. [Pedro, ch. 40: 55-58]
Chronicle entries in which Pedro I, King of Castile appears:
Crónica de D. Pedro, ch. 15: 1, 12, 13-14, 19, 25, 29, 36, 39, 43-44, 46, 50, 53, 66, 68-69, 101, 109