Star Ocean: Blue Sphere is an action role-playing video game developed by tri-Ace and published by Enix for the Game Boy Color handheld video game console in June 2001. It is a spin-off entry in the Star Ocean series, acting as a direct sequel to the 1998 PlayStation title Star Ocean: The Second Story. It was later remade for mobile devices, releasing in 2009.

Blue Sphere is set two years after the events of The Second Story on the planet Edifice, a world currently in a pre-space flight state but holding remnants of an advance civilization. Protagonists from the events of The Second Story are brought down onto the planet by an unknown force, and must work to discover its source and leave. The gameplay carries over multiple Star Ocean elements, including real-time combat and optional side conversations between party members. New elements include item creation tied to the skill system, and local multiplayer options unlock through the Game Link Cable.

Development began in 2000 as a spin-off from the main Star Ocean series, taking approximately one year to complete. Multiple core staff from earlier Star Ocean titles returned, including series composer Motoi Sakuraba. The character designs were created by manga artist Mayumi Azuma. The production period proved difficult for the team, with the programmers collapsing from exhaustion. In addition to tri-Ace, developer tri-Crescendo helped with the sound design. Blue Sphere has garnered a positive reception from journalists, and has sold 130,000 copies in Japan as of 2007.

Star Ocean: Blue Sphere created by