Network analysis is increasingly applied throughout the social sciences. Networks have been at the core of criminological thinking since its inception. As early as Sutherland and Shaw and McKay, networks have been regarded as important causes of delinquent behavior. Networks, by definition, reflect patterns of relationships between observations. Observations are typically human actors, but can represent any criminologically relevant entity, such as gangs, grocery stores, or street corners. Networks can even represent connections between actors that occupy distinct roles (e.g., connections between people and places). This flexibility in how networks can be defined and analyzed presents innumerable promising opportunities in the analysis of crime. Networks can influence criminal behavior by influencing selection into delinquent peer networks and by transmitting delinquent values and behaviors. While some of the earliest adopters of network methods turned to analyses of peer group context and delinquency, more recent applications examine the generative forces driving criminal organization dynamics, gang violence, and even social order among prison inmates. Some other visionary research examines how networks in physical space affect the distribution of crime, and some studies now suggest that networks act as an important mechanism linking formal sanctioning to recidivism. This body of recent evidence stands in contrast to general theories of crime, which argue that networks have little causal influence on criminal behavior. In contrast, selection into delinquent peer networks amplifies criminal behavior through both learning and opportunity.