| Tello Alfonso | |
| Lord of Aguilar de Campoo | |
| Noble Family: | Castilian House of Ivrea |
| Father: | Alfonso XI of Castile |
| Mother: | Eleanor of Guzman |
| Spouse: | Juana of Lara |
| Issue: | See Issue |
| Birth Date: | 1337 |
| Death Date: | October 1370 (aged 33) |
| Religion: | Roman Catholicism |
Tello Alfonso of Castile (1337 – October 1370) was the seventh of the ten illegitimate children of Alfonso XI of Castile and Eleanor of Guzman. He was a prince of Castile and First Lord of Aguilar de Campoo. In Spanish he is known as Tello de Castilla, Infante de Castilla; Señor de Aguilar de Campoo, de Vizcaya, de Castañeda y de Lara.
He was born in Seville. He participated along with his brothers in the struggles against the despotic rule of his half-brother Pedro of Castile also known as Pedro the Cruel.
In 1353 he married Juana of Lara (daughter of Juan Núñez III de Lara), but she was reportedly murdered in 1359, on orders of King Peter (Pedro the Cruel). Tello and Juana had no legitimate children. It is reported that Tello kept the news of her death secret in order to maintain possession of her dowry.
Tello had many illegitimate children: