This book provides, from a psychological perspective, a concise critical introduction to, and assessment of, three different approaches to managing diversity: multiculturalism, assimilation, and omniculturalism. This task is undertaken in global context and with reference to cutting edge empirical psychological research. Historically, assimilation has been the dominant approach to managing diversity. However, since the late 1960s multiculturalism has gained favor and is now the most commonly adopted approach in most Western as well as in some non-Western societies. Both assimilation and multiculturalism rest on some central psychological assumptions that are not supported by empirical research. After critically reviewing the psychological foundations of assimilation and multiculturalism, it is argued that we need to explore new approaches to managing diversity in the twenty-first century. A number of contemporary research programs, such as those related to social identity theory and the common group identity model, point to omniculturalism as a more promising approach to managing diversity. Also, global warming, nuclear proliferation and other major challenges confronting humankind suggest that a diversity management approach that gives priority to human commonalities and universal rights is better suited to our contemporary needs.