This article synthesizes the cross-disciplinary literature on government transparency. It systematically reviews research addressing the topic of government transparency published between 1990 and 2015. The review uses 187 studies to address three questions: (1) What forms of transparency has the literature identified? (2) What outcomes does the literature attribute to transparency? and (3) How successful is transparency in achieving those goals? In addressing these questions, the authors review six interrelated types of transparency and nine governance- and citizen-related outcomes of transparency. Based on the findings of the analysis, the authors outline an agenda for future research on government transparency and its effects that calls for more systematically investigating the ways in which contextual conditions shape transparency outcomes, replicating studies with varying methodologies, investigating transparency in neglected countries, and paying greater attention to understudied claims of transparency such as improved decision making and management.