This chapter examines the notion of power in relation to authority and the state. Power and authority are central concepts in politics. Politics is about competing interests and values, and this requires knowing something about power, since those who have power over others can determine which interests and values will be adopted by political decision-makers. The chapter first considers the link between power and authority before discussing the classic threefold typology of authority proposed by Max Weber: traditional authority, charismatic authority, and legal–rational authority. It then explores some conceptual questions about power; for example, whether it is the same as force, or whether it must be exercised deliberately. It also evaluates the methodological problems inherent in the measurement of power, particularly in relation to the different theories of the state such as pluralism, elitism, and Marxism.