Social capital is defined as the resources accessed by individuals as a result of their membership of a network or a group. It has been linked to population health outcomes among individuals as well as collective entities (such as neighborhoods, workplaces). Indicators of social capital include the exchange of social support and information within a social network as well as the levels of trust that lubricate such exchanges. At the collective level, social capital is postulated to influence health outcomes through regulation of social behavior (informal social control), and the ability of groups to undertake collective action (collective efficacy). Social capital has the dual potential to promote health as well as to threaten health, for example, via the exclusion of outsiders. The chapter summarizes the theoretical debates over social capital as well as the state of empirical evidence. Particular attention is paid to the role of social capital in disaster resilience and recovery.