Great Sky River is a 1987 novel written by author Gregory Benford as a part of his Galactic Center Saga series of books.

Great Sky River tells the story of the Bishop family, who fight for their very existence on the planet Snowglade, which has been taken over by the Mechs.

The novel takes place during a period when the Mechs have invaded Snowglade and are slowly altering its climate to suit themselves; drying it out to protect their steel bodies from rust.

As the series progresses, it is revealed that the Bishops and related colonists are post-humans, or as the text describes them, a "fourth species of chimpanzee".

Having defeated the Mechs in the Solar System, they have traveled to near the galactic center using slower-than-light space vessels, meaning that the setting is tens of thousands of years in the future.