Amid the 2011 Arab Revolts, and the subsequent worldwide Occupy movement, social movement scholars faced sudden, powerful mass mobilisations without easily identifiable resources, networks, or forms of organisation underlying them. These instances of mobilisation beyond the scope of what we traditionally consider ‘the movement’ have stretched existing theories of social movements to their limits, defying both conventional theoretical frameworks and existing approaches. This work undertakes a novel analysis of mobilisation which accounts for these new, disruptive cases. It advances the concept of Affinity: a predisposition to participate in certain causes based on social or psychological traits. Alongside this concept, it outlines conditions of Convergence: emergent situations, frames and spaces which encourage those with such Affinity to temporarily participate in mass mobilisations. These two concepts are advanced and developed through a study of the 2011 Egyptian Revolt and Occupy Wall Street movement, alongside the classic case of the 1789 French Revolution. These cases are analysed in comparative perspective to develop a powerful analytical tool with which scholars can augment conventional analyses: The Affinity-Convergence Model of Mobilisation.