How do multiple species coexist despite the potential for competitive exclusion? Recent years have seen great strides for answering this question through the development of “modern coexistence theory”: it provides a means to test and quantify several coexistence mechanisms. Moreover, it provides a common currency that potentially integrates multiple disciplines in community ecology. Though promising, the theory is currently appreciated mostly by those who are interested in coexistence itself. This is partly because its theoretical and empirical challenges exclude newcomers from other fields in a broad range of community ecology. In this symposium, we introduce how coexistence theory can be tested and applied to answer questions originating from various topics in community ecology including plant–soil feedback, eco-evolutionary dynamics, and phytoplankton blooms. By doing so, we hope to find a way toward a modern synthesis of community ecology via coexistence theory.