This chapter provides an overview of the sociolinguistic dimensions of heritage language acquisition and use across a variety of settings. Principal theoretical concepts and methodological approaches that address macro, meso, and micro level considerations, including history, context, community, and culture as well as identity, investment, and ideology are described. It considers ‘the social turn’ in language acquisition research more broadly and explains its relationship to heritage language studies, highlighting, in particular, linguistic variability. The chapter identifies key trends in the fields of heritage language acquisition and socialization, and describes the crucial impact of social variables such as generation, social class, ethnicity and race, and gender and sexuality in processes of heritage language acquisition and use. Finally, potential future areas of research focused on the sociolinguistic realities of heritage language users and their communities are highlighted. Overall, this chapter provides readers a glimpse into the sociolinguistic complexity of heritage language speakers, learners, and their communities.