Probability Sun
| First edition | |
| Author | Nancy Kress | 
|---|---|
| Cover artist | Bob Eggleton | 
| Language | English | 
| Series | Probability trilogy | 
| Genre | Science fiction | 
| Publisher | Tor Books | 
| Publication date | 2001 | 
| Publication place | United States | 
| Media type | Print (hardback & paperback) | 
| Pages | 347 | 
| ISBN | 978-0-7653-4355-0 | 
| OCLC | 51638823 | 
| Preceded by | Probability Moon | 
| Followed by | Probability Space | 
Probability Sun is a 2001 science fiction novel by American writer Nancy Kress, a sequel to her 2000 publication Probability Moon. It was followed in 2002 by Probability Space, which won the John W. Campbell Memorial Award.
The novel concerns a military expedition to the planet World, where aliens live who have developed a strange form of telepathy or collective unconscious, "shared reality", which causes piercing "head-pain" whenever "Worlders" attempt to hold strongly differing opinions. However, the expedition concerns a crash-landed alien artifact in the planet's crust which has uncharted powers, and may be the key to humanity winning a war against the "Fallers", a genocidal alien race.