This chapter develops the concept of affective publics, starting from a critical evaluation of the normative assumptions of “the public sphere” and its inherent hierarchies and exclusions along the lines of class, race, or gender. Drawing on Zizi Papacharissi’s notion of affective publics as small, fragile, and fluid, this chapter proposes that affect is central to the constitution of publics – in the plural – and that an affective understanding of publics reveals their relational, processual, and performative character. This understanding is particularly important to account for the complex mobile media environments and new networks of communication that are constitutive of contemporary publics.