This volume offers a multidisciplinary view of cutting-edge research on bilingualism in Spanish and Portuguese-speaking regions, with the aim of building a bridge between sub-fields and approaches that often find themselves isolated from one another. The thirteen contributions in this volume offer a glimpse of the diversity of bilingualism present in the Hispanic and Lusophone world, shedding light on the sheer variety of speaker communities, language pairings (e.g., Spanish-English, Spanish-Basque, Spanish-Dutch, Portuguese-Spanish-English, Portuguese-English, Spanish-K’ichee Maya, and Spanish-Ixcatec) and speaker types (e.g., simultaneous bilinguals, and early and late sequential bilinguals).