In addition to human, animal, and artificial intelligence, there is another important kind of intelligence on our planet: the collective intelligence of groups of individuals acting collectively in ways that seem intelligent. This chapter analyzes collective intelligence in terms of what tasks are being done, who is doing them, and why and how the tasks are being done. For instance, the chapter shows how groups can have both specialized and general collective intelligence and how the collective intelligence of a group can depend on the task-relevant abilities of group members, their interpersonal abilities, their diversity, and their intrinsic or extrinsic motivations. The chapter also analyzes the factors involved in group-level processes such as deciding, creating, remembering, sensing, learning, and coordinating. Just as studying the neural basis for intelligence links neural processes to cognitive psychology, studying collective intelligence links cognitive psychology to higher-level social, organizational, and economic processes.