This chapter discusses research on police legitimacy in Western societies. It will first provide a brief history of early studies in the field, most notably from the United States, United Kingdom, and Australia. Both the antecedents and consequences of police legitimacy will also be discussed. The chapter will then be organized around studies that have pushed the boundaries of methodological and theoretical innovation in the field, specifically, (a) research highlighting differences in police legitimacy across different population groups and contexts (e.g., racial minorities vs non-minorities; immigrants vs non-immigrants; police-initiated vs citizen-initiated contacts); (b) studies that explore legitimacy in the neighborhood context; and (c) common and innovative methodological approaches used to study police legitimacy. Finally, this chapter will end with some reflections on future directions for the field.