People use the news media to learn about the world beyond their family, neighborhood, and workplace. As news consumers, we depend on what television, social media, websites, radio stations, and newspapers decide to inform us about. This is because all news media, whether through journalists or digital algorithms, select, process, and filter information to their users. Over time, the aspects that are prominent in the news media usually become prominent in public opinion. The ability of journalists to influence which issues, aspects of these issues, and persons related to these issues, are perceived as the most salient has come to be called the agenda-setting effect of journalism. First described by Maxwell McCombs and Donald Shaw in a seminal study conducted during the 1968 elections in the United States, agenda-setting theory has expanded to include several other aspects beyond the transfer of salience of issues from the media agenda to the public agenda. These aspects include: the influence of journalism on the attributes of issues and people that make news; the networks between the different elements in the media and public agendas; the determinants of the news media agenda; the psychological mechanisms that regulate agenda-setting effects; and the consequences of agenda setting on both citizens’ and policymakers’ attitudes and behaviors. As one of the most comprehensive and international theories of journalism studies available, agenda setting continues to evolve in the expanding digital media landscape.