Alien Soldier[a] is a side-scrolling run and gun video game developed by Treasure and published by Sega for the Mega Drive.

Retail copies were released in Japan and PAL territories while in North America it was only available exclusively via the Sega Channel cable service.

However, Alien Soldier puts an emphasis on challenging boss fights with short and easy levels serving as downtime in-between.

Development lasted two years and was led by Hideyuki Suganami, who originally held ambitious plans and wanted to build the entire game himself.

With the market for the Mega Drive quickly shrinking to make headway for the incoming 32-bit fifth generation hardware, Suganami received support from other Treasure staff and released the game with only about half of his original ideas realized.

Some negative critique was directed towards the hard difficulty, steep learning curve, and unorthodox gameplay, but many still recommend it to fans of Gunstar Heroes and the run and gun genre.

It was also re-released worldwide on the Wii Virtual Console in 2007, Steam in 2011, the Nintendo Switch Online + Expansion Pack in 2022 and the Sega Genesis Mini 2 in 2022.

Alien Soldier is a side-scrolling run and gun video game in which the player controls the main character, Epsilon-Eagle, through 25 stages and 26 bosses.

The player can also perform a dash across the screen, which when at full health, will become a deadly move called "Phoenix Force" that will damage any enemies in its path.

A terrorist organization known as Scarlet rose up within this race and sought to dominate the rest of the A-Humans and A-Earth by locking the planet down and keeping anyone else out.

[5] Development of Alien Soldier lasted two years and was led by Hideyuki Suganami, who from the start wanted to make the entire game himself.

[6] Treasure explicitly targeted the game for "hardcore" Mega Drive players and designed its difficulty and end-game scoring methods with this in mind.

[6] Years later, Yosuke Okunari of Treasure addressed concerns that Alien Soldier was released as an incomplete game, stating the notion is only derived from Suganami having originally had large ambitions that were never realized.

[13] The original cartridge has become rare and expensive due to low production numbers and positive word of mouth, selling for over 20,000 yen (~US$200) in used game stores by 2006.

The PlayStation 2 release includes both PAL and Japanese versions, video filter options, and a recorded full playthrough done by an expert.

[13][15] Alien Soldier was released again worldwide in fall 2007 on the Wii via the Virtual Console download service, and again for Microsoft Windows on Steam on 6 January 2011.

[20] Frank Provo of GameSpot reviewed the Wii Virtual Console release in 2007, citing the excellent graphics, sound, and general intensity of the game.