This article is an introduction to a special issue on ethnography, diversity and urban space. It places the ‘diversity turn’ within studies of migration and multiculture historically and discusses the implications of concepts such as ‘diversity’ and more recently ‘super-diversity’ for scholarship, policy and identity politics. It argues that diversity is a helpful concept for studies of migration and multiculture because it avoids the essentialism and bias towards ethnic affiliation often characterising studies within the multiculturalism framework, while being more grounded locally than studies within the transnationalism framework. It examines the methodological implications of increasing diversity and complexity on ethnographic studies and the definition of the ‘field’. It makes the point that increasing urban diversity poses a challenge to ethnographic ideals of ‘immersion’ and wholeness. Finally, it introduces the individual articles in the special issue.