Mega Man X4 is the series first true outing on the Sony Playstation, its first entry into the polygonal 32-bit world. This discounts the rare and mostly unheard of Mega Man X3 release on the Sega Saturn and Sony Playstation as it was merely a port of a Super NES game.

After X3's events, the world again became peaceful. The Maverick Hunters were joined by a military unit called the Repliforce, led by the cleverly named 'General.' The exact purpose of the Repliforce is left a bit uncertain in the game, but they're a large armed force stocked with (obviously) Reploids.

Everything is peaceful... until Mavericks attack the Sky Lagoon! Then either X or Zero (your choice) rush to the scene to investigate. They find another Maverick Hunter, Magma Dragoon, at the scene, just in time for the Sky Lagoon to fall onto the city below.