Social media encompass web-based programs and user-generated content that allow people to communicate and collaborate via mobile phones, computers, and other communication technologies. Unlike other media linked to a particular technology, social media are a phenomenon associated with a set of tools, practices, and ideologies for connecting and collaborating. Social media blur distinctions between one-to-many and face-to-face communication. They allow individuals and groups to connect across boundaries of space and time, both synchronously and asynchronously. Afforded by changing technology, social media are ever-expanding as users develop novel uses and creative content. Scholars have studied social media across a range of topics, including such issues as message content and construction, identity formation, relationship development, community development, political activism, disinformation, and cyber threats. Social media vary culturally. For instance, in China social media are impacted by internet censorship, including not only the kinds of apps that are used in China—WeChat and Weibo instead of Facebook and Twitter—but also forms of expression and online activities. While Chinese social media can be a site for political activism, and creative, humorous, and satirical messages, they are constructed in ways that avoid online censorship. Social media also afford the construction and maintenance of local communities and cultural identities. For instance, users with a shared interest, occupation, activity, or offline connection, such as a hometown, may communicate online using a shared language, vocabulary, or code. Hence, unlike mass media that can promote a collective, national identity, social media may facilitate the re-emergence and construction of local and diverse identities. Finally, social media can empower subaltern individuals and groups to mobilize and effect change through collective action. Yet social media, when employed by the state and/or neoliberal corporate powers, can work to suppress subaltern groups by co-opting social media as a technology that affords surveillance. They may also be used to spread misinformation or extremism by both state-sponsored and non-state actors.