Twi'leks are head-tailed alien humanoids from the planet Ryloth. Sometimes, the female Twi'leks serve the Hutts as dancers.
During the age of the Old Republic, Ryloth and the Twi'leks were part of the Galactic Republic, and were represented by senator Orn Free Ta. However, when the Galactic Empire rose to power, Ryloth's people rebelled. Palpatine and Darth Vader personally routed this insurrection when they attacked the planet. Afterwards, Ryloth's people were enslaved. Twi'leks would later join the New Republic when the Rebel Alliance defeated the Empire at the Battle of Endor.