The privatization of security understood as both the top-down decision to outsource military and security-related tasks to private firms and the bottom-up activities of armed non-state actors such as rebel opposition groups, insurgents, militias, and warlord factions has implications for the state's monopoly on the legitimate use of force. Both top-down and bottom-up privatization have significant consequences for effective, democratically accountable security sector governance as well as on opportunities for security sector reform across a range of different reform contexts. This volume situates security privatization within a broader policy framework, considers several relevant national and regional contexts, and analyzes different modes of regulation and control relating to a phenomenon with deep historical roots but also strong links to more recent trends of globalization and transnationalization. Alan Bryden is deputy head of research at the Geneva Centre for the Democratic Control of Armed Forces (DCAF). Marina Caparini is senior research fellow at the Geneva Centre for the Democratic Control of Armed Forces (DCAF).