"Sai Dai Oh" (獣拳巨神サイダイオー, Jūken Kyojin SaiDaiOh — "Beast Fist Giant God") is the battle form of the Juken God SaiDain, a colossal rhinoceros that Master ShaFu carved from stone and which houses the Fierce Ki soul of the legendary Bruce E. (a loving nod to Bruce Lee). It is summoned with the SouJuuTou, a sword-like calling weapon wielded by Ken Hisatsu / GekiChopper — though in a pinch all of the Gekirangers can pilot it together. Considerably larger and rawer in brute strength than the other GekiBeasts, SaiDain marks the team's leap to its next tier of power in Juken Sentai Gekiranger.

Reared up into SaiDaiOh, the giant brings its full arsenal to bear: a faceplate folds over the head for its Defense Mode, the rhino horn reshapes into the mighty SaiDaiKen (Break Big Sword) for attack, and the beast's armored back becomes a shield. At roughly 70 m tall, 3,800 tons and a power output of 3,500 it ranks among the most massive mecha in the show — but its real trick is the ability to gather and amplify the power of entire sets of GekiBeasts.

That gift fuels its spectacular super-combinations: joining GekiWolf and GekiTohja it becomes SaiDaiGekiTohja, with GekiWolf and GekiFire the fiery SaiDaiGekiFire, and in episode 47 the seven-beast juggernaut SaiDaiGekiRinTohja. Each form caps off a thunderous finisher, making SaiDain the centerpiece of the team's most powerful finishing moves.

As a toy it debuted in 2007 from Bandai Japan as the "Juken Kyojin DX SaiDaiOh" — a large premium box set with electronic light-and-sound gimmicks (needs two C batteries) plus the roughly 28 cm SouJuuTou calling weapon, and it docks straight onto the DX GekiTohja and GekiFire figures. For the Western market Bandai America released the mold under Power Rangers Jungle Fury as the "Rhino Steel Megazord" (in the show the Rhino Steel Zord / Rhino Pride Warrior Mode of Dominic, the Rhino Ranger, from Fall 2008) — a smaller, simplified all-plastic take on the Japanese DX that also saw a Disney Store exclusive edition. An absolute collector highlight and one of the most imposing auxiliary mecha of its era.