This paper was published in the journal Culture and Religion in 2007. Although the term multiculturalism is often understood on the public level as an ideology or as a social programme (to be ‘for’ or ‘against’), I argue in this paper that the term should also be understood to refer to the complex range of issues associated with cultural and religious diversity in society, and the social management of the challenges and opportunities such diversity offers. Understood in this sense, multiculturalism is not an optional extra, it is not something that a society can choose to have or avoid. For any country without closed borders then multiculturalism is a fact of today—it is present within the society. What is important are the social and political responses to the cultural and religious diversity that results from transnational flows and settlement of people. This introduction to the collection of papers highlights the need to understand multiculturalism as a process which is always contextual, and the role that state management of difference in the successful development of diversity plays.