This chapter is the first to consider the private security industry and policing. It begins by exploring what is meant by the term ‘private security’. The chapter then examines the key segments of the industry. It provides a taxonomy of the sector and others, offering a new distinction between the ‘old’ private security industry, built upon uniformed guards, private investigators etc, and the ‘new private security industry’ built upon cyber security-related activities. The size of the industry in different countries and the largest private security companies are also considered. The chapter ends with a general overview of the contribution to policing of private security.