Killzone is a series of first-person shooter and twin sticks shooter video games for Sony Interactive Entertainment's (SIE) video game consoles. The main series and the PlayStation Portable (PSP) installment were developed by Guerrilla Games, a subsidiary of SIE, and the PlayStation Vita installment was developed by Guerrilla Cambridge. Killzone consists of six games, beginning on the PlayStation 2 in November 2004 with Killzone, and continued on the PlayStation Portable in October 2006 with Killzone: Liberation. Killzone 2 was released for the PlayStation 3 in February 2009, and Killzone 3 was released in February 2011, also for the PlayStation 3. Killzone: Mercenary was released for the PlayStation Vita in September 2013, followed by Killzone Shadow Fall, a launch title for the PlayStation 4, in November 2013.
