Centering stances, positionalities, and style, the third wave of sociolinguistic study positions individuals at the heart of its analysis. Understood as a continuation of the first and the second waves, which sought to elucidate correlations between linguistic features and broad socio-demographic groups (first wave) or locally relevant categories and networks (second wave), the third wave focuses on the social meaning of variable linguistic features. It recognizes that speakers agentively employ the linguistic resources at their disposal to signal group memberships, construct their personae, and position themselves in interaction. However, research on the third wave has been, to the present, largely focused on the English language. Because the resulting sociocultural and linguistic biases are baked into our current understanding of why speakers select particular linguistic and stylistic features, a broader exploration of linguistic variation and social meaning in other languages is sorely needed. To tackle the questions raised by the third wave in Spanish-speaking contexts (e.g., How are social meanings linked to particular linguistic forms? How is social meaning structured? How does linguistic use affect social meaning? How do social meanings relate to one another? What is the role of social meaning in language variation and change?) we have mobilized scholars at the vanguard of Spanish sociolinguistics to share their work in this Special Issue. In doing so, we seek to further extend the third wave to the Spanish-speaking world and deepen, develop, and enrich the scope of third-wave research.