Galaxy Mega is the first and central mecha of "Denji Sentai Megaranger" (1997), the 21st Super Sentai, a show soaked in an electronic/digital theme from top to bottom. Fittingly, Galaxy Mega stands apart from most Sentai robots: rather than combining from four or five small vehicles as usual, the robot forms via "Denji Gattai" (electromagnetic fusion) from just two large spacecraft — the Mega Ship and the Mega Shuttle — merging into its upright robot mode. It is piloted by the four core Megarangers (MegaRed, MegaBlack, MegaBlue and MegaYellow), ordinary high-schoolers recruited into Ranger duty through a video-game-style selection system.

In battle Galaxy Mega favors clean, knightly sword strikes and holds its own as a dependable all-rounder against the Nejilon monsters. Its key upgrade is docking with the support mecha Delta Mega, which itself unfolds from its own shuttle/spacecraft form: together the two form the far bulkier Super Galaxy Mega, giving the team a noticeable jump in firepower and armor.

In the US adaptation "Power Rangers In Space," Galaxy Mega became the Astro Megazord. A fun wrinkle for collectors: here the ship — the Astro Megaship — doubles as the Rangers' flying home and mobile base, transforming into the Zord when the fight calls for it. Delta Mega became the Delta Megazord, and the pair's combination the Astro Delta Megazord.

The original DX toy arrived in 1997 from Bandai Japan as the "DX Denji Gattai Galaxy Mega": it reproduces the full transformation and combination of Mega Ship and Mega Shuttle into the robot, features electronic light and sound effects, and connects with the separately sold DX Delta Mega to form Super Galaxy Mega. Bandai America reissued the figure for the In Space toyline as the "Deluxe Astro Megazord," easily told apart by its lighter blue US paint — a neat point of difference from the Japanese original. Both vintage releases are prized shelf pieces today, especially complete with Delta Mega and in clean condition.