Under what conditions do successful revolutions come to be overthrown by counterrevolutions? What explains counterrevolutionary challenges, and when are they most likely to succeed? These are the questions I plan to answer in this dissertation project. I define counterrevolution as an effort in the aftermath of a successful revolution to restore a version of the pre-revolutionary political regime, and propose to conduct a book-length study of the factors that explain its emergence. Contrary to existing accounts of counterrevolution, which focus exclusively on the actions of the old regime elite, a central contention of the project is that overthrowing revolution requires a popular base. Specifically, I propose that counterrevolutions are made possible by the support of a disaffected minority player in the revolutionary coalition itself, whose enthusiasm for revolutionary change wanes as a new political order begins to take root and who comes to favor a return to the status quo ante. To make this case I will draw on quantitative and qualitative research strategies at both the cross-national and sub-national level. I will bring together techniques of process tracing and event analysis to study the case of Egypt, which experienced a political revolution in 2011 and, subsequently, a counterrevolution in 2013. I will then compare Egypt's experience to cases of more durable revolutionary regimes in the Middle East, including Iran in 1979 and Tunisia in 2011, and to two other cases of counterrevolution outside the Middle East. Finally, I will test my theory with a large-n statistical analysis of counterrevolutionary challenges across the full universe of successful revolutions in the 20th and 21st centuries. In addition to developing a novel theory of counterrevolution, this project will contribute to an emerging new generation of revolutions scholarship on post-revolutionary regime outcomes and political trajectories.