The Ystreban are an alien species native to the planet Ystre. They are a humanoid species with uniformly blue skin and a uniquely shaped skull. Unlike most humanoid species, a Ystreban's brain is contained in the lower portion of its skull, behind the mouth, while the upper portion of the head is used for sensory organs such as the nose and eyes.

During the Teraport Wars, certain factions of the Ystreban government (such as House Phica) were sympathetic to the Tausennigan Ob'Enn Empire.