In this chapter, students will learn about the concept of polarity as it relates to security studies. It reviews the origins of the concept in neorealism and its dependence on a distinction between great powers and all other states. It then looks at how polarity was used during the Cold War and post-Cold War debates in international relations (IR). Looking forward, the unipolarity debates basically set up two scenarios: either other rising powers will challenge the US as sole superpower, with a possible return to bi- or multipolarity, or the US will hang on as sole superpower, either dominating the system or increasingly having to act as primus inter pares within a group of leading powers. The chapter questions these framings, arguing that in a truly global system the simple distinction between superpowers and the rest does not work, and that the key distinction is among superpowers (globally operating), great powers (influential in more than one region) and regional powers (influential mainly within one region). This taxonomy opens the possibility of another scenario, a world with no superpowers, only great and regional ones.