In this chapter, students will learn why processes of development are relevant for security studies. It first outlines the historical roots of development and summarizes the ‘Washington Consensus’, which has dominated international approaches to development since the 1980s. It then explains how development challenges have been viewed as major security threats at three broad and interrelated levels: international, state and individual (human). The chapter then analyses some of the main ways in which development and security have been linked in theory and practice. While few would disagree with development as an aim, the ways it is pursued in practice can create or compound insecurity for some of the poorest people in society. It can also increase the likelihood of violent conflict by marginalizing some groups at the expense of others, and by providing an environment in which armed groups can access funds and materials to support their campaigns, particularly through shadow economies.