Serie ideada por Eiji Tsuburaya -experto de efectos especiales de la Toho Pictures- que narraba las aventuras de la M.J., una organización compuesta por agentes entrenados para combatir la amenaza mundial que representan los Hombre Q, membros de una organización maléfica que planenan conquistar el mundo. Los agentes de M.J., los “Magníficos Justicieros” cuentan con una gigantesca nave capaz de volar y sumergirse, y que en su interior contiene aviones y minisubmarinos para cada uno de los justicieros.

Mighty Jack was a tokusatsu SF/espionage/action TV series. Created by Japanese effects wizard Eiji Tsuburaya, the show was produced by Tsuburaya Productions and was broadcast on Fuji TV from April 6, 1968 to June 29, 1968, with a total of 13 one-hour episodes. The music for the episodes was done by Isao Tomita and Kunio Miyauchi.

Reportedly, Eiji Tsuburaya considered this series his masterwork because the focus was on the people rather than on the vehicles and special effects This focus on the people was similar to the works of Gerry Anderson, of which Eiji was a big fan. The Mighty Jack mecha/HQ featured in this series also has some similarities to Eiji's previous TV masterpiece, Ultra Seven.

Even for the original series of 13 one hour-long episodes, the ratings were low. The follow-up series, Fight! Mighty Jack, fared better in the ratings, perhaps because of its inclusion of monsters and aliens rather than purely human evil-doers like Q.