Inspired by the courage demonstrated and devastation sustained in the warfare of the 20th century, Killzone makes its debut as a PS2 exclusive, bringing with it an assortment of features. The game offers four playable characters and 27 different weapons. Players will engage the enemy in more than 11 detailed environments, designed to showcase the grueling settings of a war-ridden planet. There are several gameplay modes to chose from, including single-player and multiplayer (team-based and competitive), as well as online play for up to 12 players.

Killzone immerses players in a future of space colonization that has resulted in several planets becoming inhabited by humans. While most of the colonies united to form the ISA, a ruthless, militaristic faction known as the Helghast has secretly separated itself, and is preparing to wage all-out war. On a nearby colony known as Vecta, the city's orbital defense mysteriously goes offline, allowing the Helghast to land and deploy their troops. As a member of an elite ISA military force, the player's objective is to escort a high-ranking official to an evacuation point while avoiding an intelligent computer-controlled enemy, able to calculate threats, maintain military direction, and execute self-preservation tactics.