Planets are celestial bodies that orbit stars. They exist in the Star Ocean series as settings for the action. Voluntary travel between planets is not possible in any game other than Star Ocean: The Last Hope, and usually, the party travels between planets as the plot progresses.

Planets are mapped according to their system (Sol System for Earth, Klaus System for Klaus III and IV, Arcura System for Expel), and sector (for example, Theta Sector englobates Earth, Roak and Energy Nede, while Gamma Sector englobates Ise, Lezonia and Vendeen). These sectors are a method of division of the Milky Way and go from Alpha to Zeta. They are also classified by development, in which the UP3 takes action.

Visited planets in the series are:

• Roak and Fargett in Star Ocean: Fantastic Space Odyssey and Star Ocean: First Departure.

• Milokeenia, Expel and Energy Nede in Star Ocean: The Second Story and Star Ocean: Second Evolution.

• Edifice in Star Ocean: Blue Sphere.

• Hyda IV, Vanguard III, Elicoor II and Styx in Star Ocean: Till the End of Time.

• Aeos, En II, Lemuris, Earth, Roak and Nox Obscurus in Star Ocean: The Last Hope.