In any community that encompasses people of multiple ethnic backgrounds, we might expect to find interesting sociolinguistic variation related to ethnicity. In a majority of countries where research related to language and ethnicity has been done, though, the focus has been on bilingualism and language choice issues as part of ethnic or national identities. Studies that look at variation within a language, on the other hand, can provide a different sort of window into the construction of ethnic identity. Not everyone in a community may have access to the heritage language associated with it, so that bilingualism versus monolingualism might not ever come up as a choice for some speakers of a particular ethnicity. On the other hand, most or all of the speakers in a community may have some access to the dominant language, so that variation within or across dialects is more available as a signal of ethnicity. This chapter brings together sociolinguistic research from several multiethnic areas around the world, focusing on variation (particularly dialect variation) related to ethnicity. The role of heritage languages will also be touched on, particularly where it plays a key role in ethnic identity.