| Sancho Alfonso | |
| 1st Count of Alburquerque | |
| House: | Castilian House of Ivrea |
| Father: | Alfonso XI of Castile |
| Mother: | Leonor de Guzmán |
| Spouse: | Beatrice of Portugal |
| Issue: | Eleanor, Queen of Aragon (illeg.) Leonor Sánchez |
| Birth Date: | 1342 |
| Birth Place: | Sevilla |
| Death Date: | 19 February |
| Death Place: | Burgos |
Sancho Alfonso of Castile (1342–1374), known in Spanish as Don Sancho Alfonso de Castilla, was Infante of Castile, 1st Count of Alburquerque.
He was born in Seville as the ninth of the ten illegitimate children of Alfonso XI of Castile and Leonor de Guzmán.
He participated in a revolt of the Castilian nobles against the despotic rule of his brother, Peter of Castile.Together with his brothers Henry (future Henry II of Castile), Fadrique and Tello, Sancho fought against his half-brother Peter.
In April 1366, his brother Henry named him Count of Alburquerque, lord of Ledesma, Alba de Liste, Medellín, Tiedra and Montalbán. These lands had been confiscated from the only son of João Afonso de Albuquerque and 7th Lord of Alburquerque. In 1373, Sancho married Beatrice of Portugal, daughter of Peter I of Portugal and Inês de Castro. They had one daughter:[1] Eleanor of Alburquerque, who married Ferdinand I of Aragon.
He also had an illegitimate daughter,[1] Leonor Sánchez de Castilla, who had a liaison with her first cousin Fadrique de Castilla, 1st Duke of Benavente, illegitimate son of Henry II of Castile with mistress Beatriz Ponce de León.