The Council of Castile (Spanish: Real y Supremo Consejo de Castilla), known earlier as the Royal Council (Spanish: Consejo Real), was a ruling body and key part of the domestic government of the Crown of Castile, second only to the monarch himself.
It was established under Isabella I in 1480 as the chief body dealing with administrative and judicial matters of the realm. With the 1516 ascension of Charles I (later Charles V, Holy Roman Emperor) to the throne of both Castile and Aragon, the Royal Council came to be known as the Council of Castile because Charles was king of many dominions other than Castile, while the Council retained responsibility only over Castile.
During periods in which there was no monarch, an absent monarch, or an incompetent monarch, the Royal Council would rule as a regency council in his place. The Council weakened in the 19th century, where it was abolished and re-established several times before being dissolved permanently.