Ancillary Mercy is a science fiction novel by the American writer Ann Leckie, published in October 2015.

While searching Athoek Station's slums, Fleet Captain Breq finds someone who appears to be an ancillary from a ship that has been hiding beyond the Radch's reach for three thousand years.

Anaander captures Athoek Station and executes members of its governing body on a live newsfeed.

After this incident, Breq forges an alliance with the AI in charge of Athoek Station and begins work to disable Anaander's ships and render Station and other AIs immune to her overrides.

Kirkus Reviews says the novel "[w]raps up the story arc with plenty of room to tell many more tales in this universe" and praised the delivery of its central message as deft and meaningful.