Over the past few years, studies in political ecology and environmental justice have been increasingly connecting the commons and social movements empirically, giving shape to a new, distinctive body of research on commons movements. In our review, we first organize and synthesize empirical lessons from this body of literature. We then highlight recent theoretical efforts made by scholars to both bridge and transcend the gap between the theory of the commons and social movement theory. As we illustrate, movements can help create and strengthen commons institutions and discourses, as well as rescale them horizontally and vertically. This is particularly evident in the context of rural community-rights movements in the global South, as well as in new water and food commons movements and community-energy movements in both the global South and North. Commons institutions, in turn, can serve as the basis of social mobilization and become a key frame for social movements, as shown in the context of local environmental justice and livelihoods conflicts and anti-privatization struggles. Tensions and contradictions of commons-movement dynamics also exist and reflect trade-offs between diversity versus uniformization and organizational closure versus expansion of discourses and practices. Theoretically, there is an opportunity to cross boundaries from the theory of the commons to social movement theory and vice versa, e.g., by highlighting the role of political opportunities and framing, and biophysical factors and polycentricity, respectively. More importantly, a new commons movements theory is emerging focusing on cross-scalar organizations, the virtuous cycles between commons projects and mobilization, and the processes of commons-making. Expected final online publication date for the Annual Review of Environment and Resources, Volume 46 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.