The chapter introduces the fundamental concepts of systems thinking used in this book. We advocate for systems thinking as a framework for developing sustainable crime prevention for risky places. We detail the principal components of systems thinking used in this book, including how we define a system, what we mean by its elements, and central ideas such as interconnectedness, beneficiaries, feedback loops, leverage points, and boundaries. We then examine the city as a system through the principles of systems thinking to examine how this can be applied to risky places and crime prevention. We discuss some of the key differences between conventional and systems thinking approaches applied to the governance of risky places, emphasizing the interconnectedness of elements across the systems structures and levels of the systems across types of urban planning models. We then briefly consider the role of governance in systems thinking as applied to crime prevention in risky places.