This paper examines conceptual issues of the emer-gence and effects of collective agency. Collective agency seems to challenge the methodological individualist assumption that only individuals can act, but treating group actors, such as parliamentary committees or court cham-bers, as mere shortcuts for complex interactions among group members raises important theoretical, empirical, and normative issues. First, the paper discusses some fundamental issues of collective agency. We argue that anal-yses of collective agency must provide generative mechanisms that demon-strate how it arises from the interaction of group members. Second, the paper introduces major approaches to collective agency from analytical philosophy and sociology. They locate the source of collective agency in the formation of collective intentions through the adjustment of group members’ attitudes, in the organization of group decision processes, or in the transfer of resources to the group level, which empowers a collective actor to act in its own right. Against this backdrop, this paper offers an integrative concept of collective agency characterized in terms of the degree of autonomy and the level of re-sources controlled by a collective actor. Third, this paper introduces the con-tributions to this special issue, which tackle a broad variety of issues, includ-ing the formation and consequences of collective intentions in small and unorganized groups, collective agency issues of institutionalized groups and organizations, collective agency of large and unorganized groups without de-fined memberships, and normative issues of collective agency.