Recent decades have brought significant worldwide expansion of private supplementary tutoring. Demand is especially driven by social competition, which has intensified in the context of globalization. The main suppliers of tutoring are serving teachers, commercial enterprises, and informal providers such as university students. Private tutoring has far-reaching implications for social inequalities, especially because higher-income households can easily secure more and better tutoring than their lower-income counterparts. While private tutoring can support low-achieving students, further stretch high achievers and provide employment, it can also have a backwash effect on schooling. Further, commercial enterprises and even teachers involved in tutoring may operate with questionable business practices. Yet comparative analysis shows wide variations in the governance and regulation of tutoring. While a few governments enact tight regulations, many others have laissez-faire attitudes toward private tutoring. Stronger multi-stakeholder focus on private tutoring and more robust regulations are needed to achieve the sorts of goals envisaged by UNESCO's International Commission on the Futures of Education.