King Ferdinand VI of Spain is a character from Pirates of the Caribbean: On Stranger Tides.
King Ferdinand rules from his palace in Cadiz. After learning of the Fountain of Youth, King Ferdinand sends his most trusted agent, known only as the Spaniard, to find and destroy the Fountain, because he saw it as an abomination in the eyes of God.
During the night, two fishermen arrive at the palace of King Ferdinand, carrying a piece of cloth that contains an old man who claims to have traveled with the spanish conquistador Ponce de León. The man gives a logbook that belonged to Ponce de León to Ferdinand. Ferdinand looks page by page finding nothing, but finally discovers an ancient symbol in one of the pages. Right then, he realized that the legends of the Fountain of Youth were true. King Ferdiand then sends The Spaniard to find and destroy the Fountain.