In certain academic and ideological corners it remains dogmatic to equate mass tourism with unsustainable tourism, thereby rendering the idea of sustainable mass tourism a contradiction in terms. An associated conceit is that sustainability is the province of ‘alternative tourism’ and allied smaller-scale manifestations of tourism that deliberately eschew the principle and traits of massification. It is argued in this chapter to the contrary that sustainable mass tourism is not only not a contradiction in terms, but rather the largely unrecognized normative form of sustainable tourism. Affiliated contentions hold that all tourism, even if it does not resemble ‘mass tourism’ at the local level, exists as part of a single increasingly globalized mass tourism system, and that there are innate characteristics of massification that facilitate the attainment of sustainable outcomes. The chapter begins by outlining a three-dimensional model as to what fundamentally constitutes the ‘sustainability’ in sustainable tourism, however the latter is conceived. The next section then examines the evolution of sustainable tourism from initial contexts of mass tourism/alternative tourism polarity to repositionings of increased convergence. Enlightened mass tourism is presented as the logical culmination of amalgamation. Heavily visited protected areas and urban beach resorts are subsequently investigated as localized manifestations of mass tourism that appear to increasingly embody the ideal of sustainable or possibly even enlightened mass tourism.