While a substantial portion of political theory addresses the issue of public, formal communication&mdashparticularly in terms of its effects on democratic citizenship&mdashthere has been comparatively little scholarship that considers the political impact of informal, non-public speech. In this project, I present a theory of &ldquosocial speech&rdquo that fills in this gap, thereby providing a richer understanding of politics and the lived experience of liberal democratic citizenship. I develop this new theory in four stages. First, I begin by critiquing contemporary political theory's singular focus on public, political speech, as exemplified by deliberative democratic and Anglo-American legal theorists. Second, I look to the forefathers of liberal political speech theory (i.e. John Milton and John Stuart Mill) in order to rediscover a classical political theory of social speech. Third, building off of this foundation, I establish my own political theory of social speech, which identifies several mechanisms that explain how informal, everyday communication may affect liberal democratic citizenship and political outcomes in both positive and negative ways. Specifically, I argue that social speech: 1) develops the character traits that make for better or worse democratic citizens; 2) contributes to social capital and trust (based on mutual interests, hopes and objectives); 3) provides training for and information about one's unique political culture; and 4) forges the affective ties that determine the borders of imagined political communities. Finally, I test my theory of social speech through empirical observations and assessments of three common social speech situations: Internet speak, safe space speech and social hate speech. These case studies prove that social speech actually does affect democratic citizenship and political outcomes in accordance with the four mechanisms outlined in my theory of social speech. And because these effects may be positive or negative, depending on both the form and content of social communication, I conclude that there is a real need for political theory to develop understandings of social speech that could inform public policies to encourage democratically advantageous social speech and discourage democratically harmful social speech.