Traitor's Sun is a science fiction novel by American writers Marion Zimmer Bradley and Adrienne Martine-Barnes in the Darkover series.

While standing guard duty in Thendara, Nico Hastur, Mikhail and Marguerida's son, observes the activities of a Traveler troupe.

The next evening, while watching a Traveler show, Nico overhears two Terran operatives discussing plans to ambush the Comyn during Regis Hastur's funeral.

Nico learns from Illona that a man named Mathias, who has recently joined their troupe, is trying to stir up resentment against the Comyn with his plays.

It becomes clear that Lyle Belfontaine, the ambitious Terran station chief, intends to take military action against the Comyn during the funeral procession.

At Comyn Castle, Lew Alton, Cisco Ridenow, Valenta Elhayln, and others, await the arrival of a Terran strike force.