Despite significant advances in the disaggregation of the study of civil conflict and intra-ethnic violence, intra-ethnic violence remains understudied. In this article, we present the first systematic, cross-national analysis of the conditions that promote violent, fragmentary conflict within politically active ethnic minorities. We propose a model of intra-ethnic conflict in which collective violence is produced by the interaction between subgroup entrepreneurs and the suppressive actions of the state. This two-level model predicts a curvilinear relationship between the relative size of an ethnic minority and its probability of experiencing large-scale intra-ethnic conflict. Additional hypotheses based on the proposed causal mechanism are also posited. These hypotheses are tested with data drawn from a global sample of politically active ethnic minorities, for the period 1990 through 2006, using a combination of parametric and semi-parametric regression techniques. The results strongly confirm the predicted curvilinear relationship while also demonstrating that the specific shape of this relationship shifts in predictable ways under varying social and political contexts.