Darius is a two-dimensional horizontally scrolling shoot 'em up set in a fictional future. Uniquely among shoot 'em ups, the game's screen is three times wider than conventional size, and the arcade cabinet uses an arrangement of three screens to accommodate it. The player controls an ornate fighter spacecraft, named the Silver Hawk, and must navigate through scrolling terrain while battling a variety of fighter craft, ground vehicles, turrets, and other obstacles throughout the game's stages (referred to as zones in the game). The ship's arsenal consists of forward-firing missiles, aerial bombs and a protective force field, all of which can be upgraded by power-ups (in the form of large, colored orbs) that are dropped by specially-colored enemies throughout the game's zones. When the player reaches the end of a zone, a boss appears, which must be defeated to proceed. Once the boss of a zone is destroyed, the player is given a choice of which zone to play next via a branching path. While there are 28 zones in total, only seven can be played in a single run.

A Sega Mega Drive port was produced in 2019 that is pre-installed in the Mega Drive Mini as a bonus game.

Darius, Year 201. Invasion!

The vicious Belsar have attacked the peaceful Darius system, which now faces absolute devastation at their abominable hands! Darius' defense fighters proved no match for the overwhelming firepower of the alien forces, which wiped out their entire fleet in one fell swoop!

With nothing left to protect them, the people could only sit and wait for the icy embrace of death as the satellite bombardments continued unopposed. The scent of despair hung thickly in the air, all hope of survival having been quashed.

But then, from out of the darkness of the mourning clouds came a single bright light in the sky.

"Silverhawk........."

Like a phoenix brought forth from the embers of a burning world, the bird shaped visage became a beacon of the planet's last fight for survival! Perhaps the end is not as nigh as it first appeared.