Fidel Castaño Gil was an AUC paramilitary leader during the Colombian conflict and the brother of Carlos Castaño Gil.

Fidel Castaño Gil was the son of Jesus Castaño and the brother of Carlos Castaño Gil and Vicente Castaño Gil. Their landholding father was taken by FARC in 1981 and beaten to death when his sons could not afford to pay the whole $50,000,000 ransom, leading to the sons joining the Colombian Army and taking part in the fight against FARC. In 1982, Fidel murdered their father's killer Conrado Ramirez as he left his hotel. Fidel became known as "El Rambo" for leading troops from the front lines, and he formed the AUC vigilante and paramilitary group with his brothers. He joined forces with Moncada Cartel and Cali Cartel in order to start a bloody war against Pablo Escobar´s Medellin Cartel. They were known as los Pepes.