John Varley is a science fiction author. He has written several novels and numerous short stories, many of them in a future history (the Eight Worlds) where years before a race of mysterious and omnipotent aliens kicked humans off the Earth, but humans have inhabited virtually every other corner of the solar system, often through the use of wild biological modifications partially learned from eavesdropping on alien communications. His detailed speculations on the ways humans might use advances in biological science were revelatory in the 1970's when his story collection The Persistence of Vision was released. The title story in that collection won the Hugo and Nebula awards, and it has been suggested that "Overdrawn at the Memory Bank" may have inspired some portions of the movie Total Recall (although the primary inspiration was clearly the credited source, the Philip K. Dick story "We Can Remember it for you Wholesale").

Varley is often compared to Robert Heinlein. In addition to a similarly descriptive writing style, similarities include free societies and free love.

Varley is noteworthy for the frequent prominence of female characters, unusual in science fiction, and especially so among male authors of hard science fiction. This prominence is not only visible in his Eight Worlds history where sex changes are routine, but in his other works as well. The idea of routine sex changes are also an example of the sexual themes that color his works without dominating them.

John Varley has also written a trilogy of novels set in a hollow world reminiscent in structure to a very large Stanford torus space habitat, but with a distinctly different personality. They are:

• Titan
• Wizard
• Demon