Blackwater USA, renamed Blackwater Worldwide (2007), rebranded as Xe Services LLC (2009), and most recently renamed Academi (2011), is the world’s largest, most powerful, and best known private security/military company (PSC/PMC), offering manifold services (above all, military training, security guards and patrols, intelligence, and consulting) to both government and private clients. It has been emblematic of the character, developments, and consequences of the outsourcing of war and security. This entry discusses the origins of Blackwater, its subsidiaries and facilities, the role of Blackwater in the Global War on Terrorism and as a U.S. government contractor, and controversies and accusations.