Esteban (voiced by Shiraz Adam (English), Masako Nozawa (Japanese)) – An orphan who was rescued at sea as a young child by the Spanish navigator Mendoza. He wears one of the two sun medallions. He dreams of adventure and is very impulsive. Esteban has a fear of heights which is confounded by the people of Barcelona who believe him to be the "Child of the Sun" and hoist him up high at the port to call out the sun to aid the departing ships. He joins the Spaniards in their search for one of The Seven Cities of Gold in the New World, hoping to find his father. Upon meeting a friend of his father in China, Esteban is revealed to be a descendant of the civilazation of Atlantis, the ancient enemy of the Mu (Hiva) empire.
Zia (voiced by Janice Chaikelson (English), Rei Sakuma (Japanese)) – The daughter of an Incan high priest. She was kidnapped from Peru by the Spanish invaders and given as a present to the Queen of Spain. She met Esteban when she was taken by Governor Pizarro who wanted her to read the golden quipu. Zia wears a sun medallion like Esteban's, with an interlocking sun and moon disc.
Tao (voiced by Adrian Knight (English), Junko Hori (Japanese) – The last living descendant of the sunken empire of Mu (Hiva in the Season One English dub). He lived alone on the Galápagos Islands following the death of his father. Initially he is evasive to the others' company when they wash up on his island, but when the ship Solaris was revealed he joined them on their journey.
Kokapetl (voiced by Vlasta Vrána (English) – Tao's pet parrot who interjects conversations every so often and warns the group of danger. Kokapetl was named Pichu in the French version.
Mendoza (voiced by Howard Ryshpan (English), Isao Sasaki (Japanese) – A Spaniard, navigator for the Spanish fleet. He rescued a young Esteban from a shipwreck during one of his voyages. An experienced sailor, a proficient navigator and a master swordsman, Mendoza places himself in the role of a leader. It is not always clear, however, where his loyalties lie and as such he is often at odds with the other characters. He is accompanied by two mercenaries, Sancho and Pedro. Mendoza has spent many years searching for information about the Mysterious Cities of Gold, which eventually led him to the sun medallions- one of which he took from Esteban when rescuing him for safe keeping.
Sancho (voiced by Terrence Labrosse (English), Takeshi Aono (Japanese) – Portly associate of Mendoza. Sancho is a bit slow and stutters a lot. He and Pedro frequently tend to get into trouble together, usually when their greed gets the better of them. As such, they act as comic relief for the majority of the series. Although both he and Pedro complain frequently, they are loyal to Mendoza and follow him despite their constant misgivings.
Pedro (voiced by Michael Rudder (English), Kaneta Kimotsuki (Japanese)) – Skinny and loud-mouthed associate of Mendoza. Pedro is very cautious and easily scared, but can often be swayed into action by the promise of gold. Despite his cowardice Pedro engages often in battles, usually teamed with Sancho.
Papacamayo – Zia's father and the chief of the Mayan Village of the New Sun.
Atanos (The High Priest) – Esteban's father and the High Priest, guardian of the City of Gold and keeper of the Great Library. Mendoza knows he is Esteban's father but did not tell Esteban so to not cause him grief. Also known elsewhere as 'The Travelling Prophet,' prior to taking up the position of High Priest at the first city, he traveled the Earth in search of more information regarding the seven cities of gold.
Commander Gomez (voiced by Matt Birman (English), Goro Naya (Japanese) – Greedy and vicious commander of the Spanish armed forces who is ruthless in his task of serving Governor Pizarro and the pursuit of Esteban and Zia.
Captain Gaspard (voiced by A.J. Henderson (English) – Sycophantically loyal subordinate of Señor Gomez. He is the Captain of the Guard, commanding a large number of Spanish soldiers. He is uncouth and rather unintelligent but has a firm command of his troops and is physically very strong. In the long term, gold and loyalty to Gomez are the only things that interest him.
Governor Pizarro (voiced by Maurice Podbrey (English), Katsunosuke Hori (Japanese) – Pizarro is the appointed governor of the entire invaded region of South America. He commands the Spanish invasion forces, including Señor Gomez and Captain Gaspard. He is a ruthless and avaricious despotic commander who holds little value for others' lives unless they serve to aid his purpose.
Menator (voiced by Richard Dumont) – Aging leader of the Olmec race. He plans to use the technology of the Cities of Gold to harness the power of the Sun and save the Olmec race from extinction.
Kalmec (voiced by Dean Hagopian) – Second-in-command of the Olmecs. He is in charge of the Olmec army and the defense of the Mountain of the Burning Shield. He is treacherous and merciless, believing in the total supremacy of the Olmecs.
The Doctor (voiced by Walter Massey) – A Spanish doctor whose real name is Fernando LaGuerra. He seems to specialize in poisons. He is searching for the Cities of Gold together with Marinche and Tetiola.
Marinche (voiced by Jane Woods) – Guide and adviser to The Doctor. She is rarely seen without the huge Tetiola, her loyal and protective slave of whom she is very fond, more so than she is of The Doctor. She appears to be a great influence on The Doctor, often manipulating him into doing things he otherwise would not do in pursuit of the Cities of Gold.