Galactor is the primary antagonistic force in the original Gatchaman anime series. It is not a single individual but a vast, technologically advanced terrorist organization dedicated to controlling the Earth's natural resources and eventually conquering or destroying the planet. The exact origins of Galactor are largely unknown, though it is believed to have existed as a conventional criminal organization for years before launching a campaign of spectacular open attacks using powerful war machines. The group is led by an alien mastermind known as Sosai X, a mysterious and disembodied entity whose true form is rarely seen. Sosai X is the supreme overlord who transformed Galactor from a simple crime syndicate into a global threat. His ultimate goal shifts over time; initially seeking to conquer Earth for his alien race, he later decides to destroy the planet entirely upon learning that his homeworld has been destroyed.

The public face of Galactor is a human subordinate who carries out Sosai X's will. The most notable of these commanders is Berg Katse, a tragic and complex figure created by Sosai X from the fusion of fraternal twins in the womb. This origin gives Katse a unique physiology, making him prone to changing sex and granting him the ability to become a master of disguise. Katse is portrayed as a ruthless and brilliant strategist, but also a deeply tormented individual who is manipulated by Sosai X's promises of being a superior being. Upon realizing he is merely a disposable pawn, Katse ultimately chooses suicide over living as a freak of nature. In subsequent series, other commanders are placed in charge, such as Gel Sadora, a young girl artificially aged into an adult leader, and Count Egobossler, a dictator who rules with an iron fist and harbors a deep distrust for Sosai Z, the regenerated form of the original alien leader.

Below the commander, Galactor is organized into a strict hierarchy of captains and millions of masked troops. The standard foot soldiers are known for their distinctive cat-like uniforms, while special forces, such as ninja units, are sometimes deployed to counter the Science Ninja Team. The organization operates with ruthless discipline, where failure is almost always punished by death, and all personnel are considered strictly expendable. Galactor boasts seemingly limitless resources and incredibly advanced technology, allowing it to construct a wide array of gigantic, animal-themed mecha that are more than a match for conventional military forces. These war machines are central to their schemes, which range from stealing uranium to creating artificial storms. The organization's role in the story is to serve as the direct and persistent antagonist to the Science Ninja Team, constantly devising new plots that force the Gatchaman to intervene in order to protect the planet.