Old Man's War is a military science fiction and debut novel by John Scalzi published in 2005. It was nominated for the Hugo Award for Best Novel in 2006. It was optioned by Paramount Pictures in 2011.
Old Man's War is about a soldier named John Perry and his exploits in the Colonial Defense Forces (CDF). The first-person narrative is similar in overall structure to Robert A. Heinlein's Starship Troopers and Joe Haldeman's The Forever War as it follows Perry's military career from CDF recruit to the rank of captain. It is set in a universe heavily populated with life forms (much like David Brin's Uplift Universe), and human colonists must compete for the scarce planets that are suitable for sustaining life. As a result, Perry must learn to fight a wide variety of aliens. While the soldiers in Starship Troopers and The Forever War relied on powered body armor to gain advantage over the aliens, the characters in Old Man's War have enhanced DNA and nanotechnology, giving them advantages in strength, speed, endurance, and situational awareness.