At the transnational level, a variety of private policing forms have emerged to protect new sites of private authority within global governance, as well as to assume security responsibilities that were previously the sole preserve of state agents. Operating across the world's most hostile regions, the transnational security consultancy industry provides a compelling example of this phenomenon. From Colombia to Iraq, leading firms deploy a wide range of specialised security services to protect client interests in high-risk environments. In this detailed examination and theorisation of transnational security consultancy, Conor O'Reilly presents a timely critique of an industry that is well-placed to harness contemporary global security anxieties. Mass casualty terrorist attacks such as 9/11, corporate scandals such as Enron, ongoing conflicts in Afghanistan and Iraq and the insecurity surrounding pandemics have all lent further impetus to the transnational ascendancy of leading security consultancy firms. Through in-depth examination of the expanding transnational policing remit of leading firms, this book provides novel insights into transnational security governance and promotes a more nuanced appreciation of the transnational commercial security field. By proposing the concept of state-corporate symbiosis, it further examines the role of transnational security consultancy firms in the pursuit of mutually beneficial objectives across the state-corporate security nexus, as well as across borders.