English has entered into the language ecologies of Southeast Asia (SEA) in one of two ways: as a former colonial language in countries like Singapore, Malaysia, or the Philippines, or as a language of globalization and internationalization. Whichever is the case, English is used within complex and diverse local ecologies that have shaped the form, function, and status of English in the region. This chapter will describe the sociohistorical features of English in the regions and the range of linguistic and cultural diversity in Southeast Asia. The chapter will then describe each of the chapters that make up the volume.