Pacheco (1419–1474), also known as the Marquis of Villena, was one of the most important noblemen at the court of Castile. He was born in Belmonte. His parents were Alfonso Téllez Giron and Maria Pacheco. The Pacheco family originated from Portugal. He grew up alongside Enrique, who would later become King Enrique IV.

He was constantly involved in intrigues. In 1460, he joined the League of Tudela—an alliance led by John II of Aragon against Enrique IV—but ultimately betrayed the conspiracy at the last moment. He also took part in the Liga de Burgos (1464) and the Farsa de Ávila (1465).

He was appointed Marquis of Villena by King Juan II because he had fought on the side of Enrique IV in the First Battle of Olmedo. He was the first person ever to receive the title of marquis from a Spanish monarch.

After the first Battle of Olmedo and the marriage of King John II of Castile to Isabella of Portugal, the power of Álvaro de Luna diminished, while the faction of Enrique and Pacheco gained influence. In the conflict between Juan II and his son Enrique, Pacheco mediated on Enrique’s behalf, while Álvaro represented the king.