| 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 the ninth of the ten illegitimate children of Alfonso XI of Castile and Leonor de Guzmán.
He was born in Seville. He participated in a revolt of the Castilian nobles against the despotic rule of his brother, Peter of Castile.
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.