In this chapter, we review sociological theories of stratification. We begin at the macro level, where we discuss theories of inequality between countries, which include the early geographical concentration of technological innovations associated with the industrial revolution and colonization. We then transition to explanations for inequality within countries, where we discuss "general" theories of national income inequality before turning to a discussion of inequalities arising from race, gender and class-based sources of inequality. In the concluding section, we call for a greater focus at the international level and for theories that develop a greater appreciation for the way that micro and macro determinants of inequality interact.