This chapter provides a broad introduction to the societal problem of crime. After first addressing the pros and cons of different sources of crime statistics, we proceed with a discussion of international variation in crime levels as well as trends over time in the incidence of different types of crimes. Among other things, we point to the decline in crime levels that has been taking place in many Western countries since the 1990s, and we consider this trend in greater detail for the case of the US. Subsequently, we provide an overview of a selection of theories that aim to explain criminal behaviour. Among other things, we examine the influence of economic prosperity and inequality on crime. We also speak to the question of what actions can be taken by governments to reduce criminality, drawing a connection with different criminological theories. As a case study, we consider the legalization of drugs as a potential solution to drug criminality. We then zoom in on organized crime as a branch of crime that operates in its own distinct way. Finally, we discuss the recent rise of cybercrime and the challenges it raises.