‘Polarization’ is a widespread diagnosis in debates of contemporary societies and is often highlighted as a substantial problem for democracy. However, few studies theorize or systematically analyze how different dimensions of polarization evolve in media communication. This entry summarizes different theoretical and empirical perspectives on polarization in political science and communication studies, potentially culminating in the disruption of the public sphere. The entry is composed of four parts: First, we introduce polarization in societal communication as (1) disruption of the public sphere. We then discuss concepts and measures of (2) ideological polarization and (3) affective polarization in media debates as parts of this process, emerging in communication through statements and networked interactions. Finally, we introduce (4) discursive polarization as the broader phenomenon that arises from the interplay of these different dimensions of polarization.