• '''''' - Atom's classmate, a very positive and outgoing young student who is very devoted to his friends. He is the class president and also the smartest. • '''''' - A recurring antagonist. He is an egotistical
mad scientist, but his villainous schemes are usually comical. He once invented a wacky machine, causing all machines to go out of control. • '''''' - A recurring antagonist, a tough imposing man usually associated with big business or the law. •
The Blue Knight - A blue suited robot who is hailed as a hero among many robots for helping those who were treated poorly by humans. He wields a sword whose aura weakens robots that refuse to rebel against humans, but does not affect rebellious robots like himself. He tends to be cold and cruel towards humans, especially those who mistreat robots, making him feared among humans. He does not care if he hurts anyone whether they are innocent or not. This is due to his past. The Blue Knight was originally created as the Blue Bon and had a younger sister named Maria. She became the bride of a human named Count Burg who abused and eventually destroyed her. Blue Bon went insane with grief and left to pursue his dream of building a nation where robots can be free. • '''''' - Deceased wife of Dr. Tenma and mother of Tobio Tenma. Hoshie was the model for Astro Boy's robot mother. • '''''' - An antagonistic circus ringmaster who buys Astro from Dr. Tenma. He is cruel towards Astro and other robots. Dr. Ochanomizu meets him in the hospital, taking Astro away, much to Hamegg's dismay. • '''''' - A robot who resembles Frankenstein's monster. He used to be a dangerous robot, until Astro Boy turned him into a good guy. • '''''' - A half-lion, half-human robot. Although Astro Boy thought that the Sphinx was attacking him, she was only trying to protect Dr. Snow from thieves. •
Pook / Bobo (dub) - A robot who can transform into any shape. He was invented by Dr. I. M. Sinister. Damaged in a fight with Astro Boy, his transformation mechanism malfunctioned leaving him in a part-lion, part-duck, part-bear, part-eagle, part-frog, formed robot. • '''''' - A criminal who uses Denkou for dastardly crimes and to release his old friends. Just when he is about to escape, while Astro Boy defeats his gang, Higeoyaji stops him in his tracks and beats him up. • '''''' - A robot who can turn invisible. Denkou was originally made by a scientist, but got stolen by the gangster Skunk Kusai, who sought to use Denkou for criminal purposes. Denkou had no concept of good or bad because of his initial upbringing under the criminal. Denkou was so naive that he allowed Skunk Kusai to attach a bomb-rigged belt onto them as part of the "game", only saved at the last minute by Astro. • '''''' - An evil robot who kidnaps Princess Lollipop and punishes the other robots. Astro Boy rescued the princess and vanquished Saturn. •
Princess Odette / Princess Lollipop (dub) - A robot swan who can turn back into her normal self when everyone's asleep. She ran away from Hullabaloo Land so she can get away from Saturn. After Saturn and his creator are defeated, Princess Lollipop returned to her swan self and flew off in the blue sky. She is based on the character of the same name from
Swan Lake. • '''''' - A robot sun with octopus tentacles. Years ago, Dr. Ochanomizu invented the Artificial Sun for the planet Mars, then decided to reject the robot sun, but it was stolen by Kin Sankaku to threaten Earth. The sun was later destroyed by Astro Boy. • '''''' - A robot centipede disguised as 47 wrestling robots. After it caused havoc on a ship and in the ocean, Astro Boy destroyed it and saved the people. • '''''' - A giant cosmic robot who came from a faraway planet. He landed on Earth as a meteor-shaped twisted pile of parts and Astro Boy and the scientists reconstructed him. During a thunderstorm, Garon revived. A corrupt scientist captured him and took him to a remote island in the Pacific Ocean, telling Garon to reconstruct the island in the image of his home planet, which Garon took to immediately. However, during his reconstruction of the island, he also began changing the atmosphere to match that of the planet, which turned out to be toxic to life on Earth. Astro managed to trick Garon to change the gravitational pull of the island to match that of his planet to complete the effect, causing Garon to hurl himself into space (his planet has a much lower gravitational pull than Earth). •
Kino / Abracadabra (dub) - A robot magician who puts on a great show for everyone, until a strange magician named Tenpercent wishes to know how Kino did his trick. Kino refuses knowing that the knowledge will be used for evil purposes. The man in response frames him for stealing art paintings from a museum. With Astro's help Kino provided the evidence that he was framed, and Tenpercent is arrested. • '''''' - The robot president of Guravia. He is the first robot to lead a nation, and is popular among his citizens. However, President Rag's good nature has made numerous anti-robot resistors want him dead. • '''''' - A robot created by Dr. Ratsburton to fool the crimson brotherhood and the entire country of Egypt that she was brought back to life by the god Isis. Cleopatra along with her inventor were killed by a cave-in after Dr. Rasburton's plan failed. • '''''' - A robot bird who destroys ships. •
Montblanc - One of the 7 strongest robots in the world. A robot mountain guide from Switzerland who is friends with Brando. While chopping wood, he met and was destroyed by Pluto. •
North #2 / Monar (dub) - One of the 7 strongest robots in the world. A robot butler from Scotland with six arms and six weapons. He was last seen killed by Pluto before he had the chance to finish him off. •
Brando - One of the 7 strongest robots in the world. A giant wrestling robot from Turkey who is friends with Montblanc and fights Pluto to avenge him. He is a big burly robot that has the ability to spin at high velocity and turn into a deadly sphere that grinds up anything it comes in contact with. Although he managed to damage Pluto, he was destroyed by him. •
Gesicht - One of the 7 strongest robots in the world. A robot detective from Germany who is made of indestructible zirconium, which also protects him from Pluto's deadly electric horns. He was assigned to arrest Pluto, but ended up destroyed by him when he was caught on Pluto's horns; Pluto merely pulled his horns in opposite directions to rip Gesicht's body in two. •
Hercules - One of the 7 strongest robots in the world. A robot gladiator from Greece. As an honorable warrior, he did not step down from Pluto's challenge, despite Epsilon's pleas. •
Epsilon / Photar (dub) - One of the 7 strongest robots in the world. In the original manga and 1963 anime, Epsilon is male. Being solar powered, he has nearly infinite power. Pluto took advantage of this and fought Epsilon during a thunderstorm, where the sun was blotted by thick clouds. Epsilon ran low on power and was eventually destroyed by Pluto. In the 2003 series he is reimagined as a female caretaker who protects Metro City's wildlife, most notably the marine animals. •
Bora - A mysterious and extremely strong robot with 2,000,000 horsepower. He can launch a destructive
katabatic wind simply by screaming his own name. He is the robot who finally defeats Pluto, who sacrificed himself to save Astro Boy from almost certain destruction. • '''''' - A robot who is in love with Robiette and does not like fighting. He and his brothers were created by Dr. Ijio. He was last seen with Robiette smashed, though their hearts are still beating. He is based on Romeo from
Romeo and Juliet. • '''''' - Chibolt's sister who has butterfly wings and is in love with Robio. She was last seen with Robio smashed, though their hearts are still beating. She is based on Juliet from Romeo and Juliet. •
Chibolt - A robot who is Robio's rival and Robiette's brother. He exploded after he and Astro had a duel. He is based on Tybalt from Romeo and Juliet. • '''''' - A robot created by Dr. Ram. He adds the Omega Factor which would allow Atlas to defy the laws of robotics (which disallowed him from hurting humans) and commit several crimes. However, Atlas turns against his creator and leaves him to be burned by the flowing lava caused by an artificial volcanic eruption, but Astro manages to defeat Atlas. •
Dr. Ram / Don Tay (dub) - An Incan scientist who hates civilization. He invented Atlas to get revenge on a village in Mexico. Atlas turns against him and leaves him to be burned in the flowing lava caused by an artificial volcanic eruption. However, Astro manages to beat Atlas and save Dr. Ram, who realizes that destroying civilization is wrong. •
Black Lux / Sharkey Dirk (dub) - A man who leads a vendetta against robots. Black Lux and his gang set to destroy all robots, who he believed caused his mother's death. In the end, Astro found his missing mother, who turned out to be a robot herself who adopted the abandoned baby. Realizing his mistake, Black Lux reunited with his mom and vowed never to destroy any more robots. • '''''' - A criminal who happens to be a president's brother. He wants to assassinate all supreme scientists and presidents who would dare get in his way. He accidentally hurts his brother, but the president eventually forgives him. •
Kin Sankaku / Elia Belial (dub) - A film producer from an island who steals the Artificial Sun. His plan was successful until Astro Boy destroyed the Artificial Sun. •
J. C. Tenpercent - A magician and inventor of Hocupocus. He and Hocuspocus are responsible for stealing art paintings and framing Kino. Tenpercent was last seen arrested by the police. • '''''' - A villain who happens to be the inventor of Rag. He kidnapped Higeoyaji and Rag while Astro Boy was searching for them. Astro Boy stopped Deadcross by disguising himself as Rag and unmasking the villain. • '''''' - A young teenager raised by robots who had him pretend to be a robot to act in their circus. The prospective mayor of Bella Notte was extremely anti-robot and after discovering Reno, took him away. However, Dr. Ochanomizu became his legal guardian and took custody of him. •
Sam Caesar - A scientist who rules a new Roman Empire. When Dr. Ochanomizu was about to escape, Brutus, invented by Caesar, caught one of the robots carrying bags full of treasure. He sent Dr. Ochanomizu to be fed by a fire-breathing robot lion. Astro Boy rescued him and defeated Caesar's entire army. He was last seen dead while Dr. Ochanomizu and Astro Boy escaped from the cave-in. • '''''' - A space crab from the Planet Gip Gip that is last seen destroyed. •
Toxor - A mist man, or gaseous being. He and other mist men possessed astronauts' body, controlling them. Toxor and the mist men were eventually frozen by Astro Boy and Dr. Ochanomizu's freeze machine. •
Koichi / Tommy Speed - A boy who rides the Silver Comet. •
Teddy Time - Dr. Time's son who befriends Astro Boy. •
Heck Ben - The son of Dr. Ben who time travels back to the American wild west. Heck Ben often appears as a cowboy in pioneer era western stories. • '''''' - A baby elephant. Astro Boy helped Pura to get back to his home after he destroyed an out of controlled robot elephant. • '''''' - An alien who is a fugitive from the planet Norico. He disguises himself as a baker, so he could get away from three scientists from his planet. He was last seen blown up with a fridge bomb on the sun. ==1980 anime only==