Cosians were a species of sentient reptilian humanoids from Cosia who had beaked mouths, four-fingered hands, eyes with lids that blinked upward instead of down, and a long tail that ended in a tuft of hair. Cosians could be Force-sensitive.

Society and culture
Cosians spoke Cosian, a trilling, chirping language. The language mingled with the sounds of their homeworld, Cosia.

Jedi Master Tera Sinube was a male Cosian who was a member of the Jedi Order. Beginning as member of the Jedi during the High Republic Era, Sinube later became a member of the Jedi High Council. Though he later left the council, Sinube went on to mentor Jedi younglings and younger Jedi such as Ahsoka Tano. In 9 BBY, Obi-Wan Kenobi encountered the corpse of Sinube in Fortress Inquisitorius on the moon Nur.

At one point, the Nu-Cosians, a genetically engineered subspecies of the Cosians, were created to colonize the planet Cos Secundu.