This edited collection interrogates the causes, processes and consequences of mass violence in the (Post-)Ottoman lands across the long twentieth century, in both Asia Minor and Southeast Europe (the Balkans). We consider here mass violence by a wide range of actors, both Muslim and Christian, state and non-state, from the preconditions through to the long-term consequences of violence. From the late nineteenth century, the Ottoman Empire came under the increasing strains of both internal upheavals and external pressure from great power rivals, culminating in the Empire's disintegration following defeat in the First World War. Increasing acts of mass violence accompanied this political instability, most notably the Armenian Genocide. We propose a collection of chapters considering the causes, processes, limitations and consequences of mass violence in the Ottoman and post-Ottoman lands, from the 1870s through to the end of the Twentieth Century. The collection brings together articles focusing on the theoretical analysis of mass violence, together with specific case studies, to consider the rhetoric mobilising violence (and its counter-narratives), the actions of Christian and Muslim state and non-state actors in support of or opposition to violence, and the reverberations of such violence over time, across (post-) Ottoman Anatolia and Southeast Europe.