Iridion 3D is a quasi-3D rail shooter video game developed by Shin'en. A launch title for the Game Boy Advance portable game console, it was released in North America on May 29, 2001 and in Europe on September 21 the same year. Influenced by the Commodore 64 game Uridium, the game features a single starship fighting the alien Iridion, who have attacked Earth. Iridion spans seven levels from Earth to the aliens' home planet, each with a fixed linear path that ends with a boss.
Iridion began development as a shooter for the Game Boy Color; when Shin'en decided to drop development and shift their focus to the Game Boy Advance, Iridion was the first game by the developer to appear on the system. Though billed as a 3D game, Shin'en used realtime encoding and resizing to manipulate the size of 2D sprites instead of creating a true 3D environment. More room on the game cartridge was available for graphics due to the game's use of the GAX Sound Engine, which allowed real-time decoding of song data in a small file size.
On release Iridion garnered generally poor reviews. The graphics and sound were generally praised; even a year after its release, critics at TechTV considered it the best-looking game on the platform. In contrast, critics derided the game's repetitive and frustrating gameplay. Despite lukewarm reception to the title upon release, Iridion 3D influenced future Shin'en shooters such as Iridion II and Nanostray.