Dr. Umataro Tenma (a.k.a. Dr. Nagamiya Tenma a.k.a. Dr. Boynton a.k.a. Dr. Balthus) is the father/creator of Astro Boy in the manga and anime by Osamu Tezuka.

Dr. Umataro Tenma (which literally means "Horse-man Heaven-horse" in Japanese) was a renowned roboticist and the Minister of Science. When his son Tobio died in a car accident, he decided to recreate him as an invincible robot. After living happily for a while with the child automaton, Tenma realized that an artificial android could not replace his son (particularly when he found out he didn't grow like a normal child) and so kicked him away; he sold him to Hamegg, a robot salesman, and he eventually ended performing in a circus where he was found and adopted by Dr. Ochanomizu, who turned him into Astro Boy.

Tenma returned several times into Astro Boy adventures. He realized that Astro was fantastic and even though his affection towards him began to return, he knew he couldn't really make amends for his behaviour. Still, he helped him as much as he could:

• he built robotic parents for Astro
• he enhanced Astro's power to a million when he fought Pluto
• he rescued him disguised as a large-hat-wearing-man when he was prisoner of a Cleopatra robot.

Tenma's original behaviour towards Astro was considered quite brutal and inhumane even for Tezuka himself, so in a newer manga edition where Astro's history restarted after his time-travel crisis (with much more detail on his education and his visit to USA with issei Taba-Koh to witness discrimination on robots by racist people), we found out that Tenma acted so harshly partly because he was drunk. Still, he then deliberately sells Astro to Hamegg, who is this time a cruel circus ringmaster who abuses his robot performers. Dr. Ochanomizu (where he is this time Tenma's arch-rival in science) has a lot of trouble to get the boy robot from him.

In the 1980 cartoon series, Tenma doesn't really reject Astro: he dismisses him for causing a mess on a boat dinner after reminding him he was a robot. Astro then gets kidnapped by corrupted circus ringmaster Hamegg while Tenma tries to find Astro back. The circus is not as harsh and Hamegg not too evil (compared to the original version), but Dr. Ochanomizu, with his assistant Chiyoko, noticing Astro Boy, has to trick Ham Egg to get Astro with him.