The Stellar Kingdom of Corill was an interstellar space-faring civilization that was led by the Corillian race and based around their homeworld of Corill II in the Corill system.
It consisted of a small group of star systems and colonies which were technologically advanced but were not populous. During the Corillian Incident, they attacked the Romulan Star Empire and were the first threat faced by the Romulans. However, despite being advanced enough to combat the Romulans, they were overwhelmed by the sheer number of their enemy. This led to the defeat and assimilation of Corill into the Romulan empire, with the last Corillian dying to the last individual in the war. Supposedly rumors erupt that a lost colony of Corillians still exist somewhere in the galaxy. (FASA RPG - The Romulans module: The Romulan Way: Game Operations Manual)