Guerrilla Games is a Dutch first-party video game developer based in Amsterdam and part of SIE Worldwide Studios. The company was founded as Lost Boys Games in January 2000 through the merger of three smaller development studios as a subsidiary of multimedia conglomerate company Lost Boys. Lost Boys Games became independent the following year and was acquired by Media Republic in 2003, renaming the studio to Guerrilla Games before being purchased by Sony Interactive Entertainment in 2005. As of March 2021, the company employs over 350 people under the leadership of joint studio heads Angie Smets, Jan-Bart van Beek, and Michiel van der Leeuw. It is best known for the Killzone and Horizon game series.