Professor Saotome discovered an extremely powerful energy emenating from the Sun, the Getter Rays. This new source of energy had the power to revolutionize the Earth and give us an unlimited source of power. To further study these rays, Prof. Saotome created three ships that could travel to space and gather information for him; Getter Eagle, Getter Jaguar, and Getter Bear. These ships, powered by the Getter Rays, could combine into a super powerful robot, Getter Robo.
Getter Robo was created for peace, but one day the Megazaur kingdom appeared and proclaimed itself the original rulers of the Earth. The Megazaur were a kingdom of dinosaurs that originally inhabited the Earth sixty five million years ago. A meteor had struck the planet and bombarded all living things in Getter Rays. Daimajin Yura, their “God,” led the survivors underground to protect them from these harmful rays. Now led by King Gora, the Megazaur claimed that since they had been the original inhabitants of the Earth, they were the true rulers of the planet. They had been lying dormant underground, waiting for a perfect time to strike. The sudden surge in Getter Rays had awakened them. Prof. Saotome realized the true potential of Getter Robo. Prof. Saotome sent out a prototype Getter Robo with three test pilots, including his son Tatsuhito. However that Getter Robo was destroyed, and the Professor's son was killed. He then entrusted the Getter machines to three new pilots, Ryoma Nagare, Hayato Jin, and Musashi Tomoe. Together, the three fought the invading swarm of Megazaur KiKaiju. By changing the configuration of the Getter Machines, Getter Robo could actually transform into three separate Robots. Getter-1, piloted by Ryoma, was an all purpose robot, and the team’s main form. Getter-1 has an average combination of speed and strength to better suit him to most situations. Getter-2, piloted by Hayato, was a sleek robot designed for speed as opposed to strength and firepower. Its drill hand allows it to destroy enemies and tunnel into the earth. Musashi piloted Getter-3, a huge tank that carried more strength and firepower than any other Getter, but at the cost of speed and agility. Prof. Saotome’s daughter, Michiru, also helps in battle by piloting a small support vessel called the Command Machine.
Mentre sta studiando le peculiarità dei misteriosi Raggi Getter per usarli come fonte di energia, il Professor Saotome si rende conto che la Terra è in gravissimo pericolo. Il popolo-rettile del Regno dei Dinosauri, rimasto in ibernazione sin dal Mesozoico, si sta risvegliando e si prepara e riconquistare il pianeta che un tempo comandava col pugno di ferro. Saotome quindi costruisce un robot alto circa 37 metri, il Getter Robot, e si mette alla ricerca di tre piloti in gradi di utilizzarne a pieno le 3 diverse configurazioni. Alla fine sono scelti Ryo(ma) Nagare, Hayato Jin e Musashi Tomoe e, con loro alla guida, il Getter Robot darà molto filo da torcere al Regno dei Dinosauri ed ai suoi terribili dinosauri-robot, i Mecha Saurus.