Ereesus was a planetary body situated within the Kanz sector, which itself was located in the Outer Rim Territories. It was also the original home of the Ereesi species.
The Ereesi were deeply involved with the practice of trading slaves, and Ereesus became a central location for flourishing slave markets. The Ereesi people launched slave raids throughout the sector in 4200 BBY. These raids, which particularly targeted the Argazdans, were the catalyst for the Argazdans to join the Galactic Republic also in 4200 BBY.
Twi'lek Tott Doneeta, before he became a Jedi apprentice, was intended to be sold with his family in the slave markets of Ereesus. However, before their captor's starship could reach the city, it was intercepted by a squad of Jedi Knights led by Arkanian Master Arca Jeth. Out of gratitude to his rescuers, Doneeta then chose to join the Jedi Order and fought throughout the Great Sith War.
The forces of the Argazdan Redoubt enacted a devastating attack on the planet Ereesus in 3970 BBY. This attack annihilated all life on the planet, including the Ereesi slavers, as retribution for their previous acts of aggression.
During the Clone Wars, a battle occurred on Ereesus. The Ereesus Planetary Security Forces and the Galactic Republic's Torrent Company fought against the Separatists.