and KeywordsThe rich research heritage on source credibility is fundamentally linked to processes of political communication and the provision of political information. Networked digital technologies, however, have recently complicated the assessment of source credibility by modifying people's ability to determine source expertise and trustworthiness, which are the foundations upon which credibility evaluations have traditionally rested. This chapter explores source credibility in online contexts by examining the credibility of digital versus traditional channels, the nature of political information conveyed by social media, and the dynamics of political information online. In addition, this chapter considers related research concerns, including the link between credibility and selective exposure, the potential for group polarization, and the role of social media in seeking and delivering credible political information. These concerns suggest challenges and opportunities as information consumers navigate the contemporary information environment in search of the knowledge to make them informed members of a politically engaged citizenry.