The World Health Organization (WHO) Commission on Social Determinants of Health (CSDH) has posed a provocative question for public health: “Why do we keep treating people for illnesses only to send them back to the conditions that created illness in the first place?”1 For the WHO Centre for Health Development (WHO Kobe Centre), hub of the Commission’s Knowledge Network on Urban Settings (KNUS), this represents a challenge to the public health sector not only to acknowledge the pervasiveness of urban poverty as a critical pathway to ill health and health inequities, but to address this as an urgent public health issue affecting a billion people living in informal settlements, or “slums.”1 People who live in informal settlements are often systematically excluded from opportunities, decent employment, security, capacity, and empowerment3 that would enable them to gain better control over their health and lives. As noted in the Interim Report by the Millennium Development Goals (MDG) Task Force, which focuses on improving the lives of urban slum dwellers: Much of urban poverty is not because of distance from infrastructure and services but from exclusion. They are excluded from the attributes of urban life that remain a monopoly of a privileged minority—political voice, secure good-quality housing, safety and the rule of law, good education, health services, decent transport, adequate incomes, access to goods and services, credit—in short, the attributes of full citizenship.4 The issue of urban poverty is not new, but it is often narrowly viewed as an economic issue that is best addressed by economic policies and interventions. Urban poverty today, as driven by globalization and rapid uncontrolled urbanization, also needs to be recognized as a social, political, and cultural process that has profound impacts on public health. Exclusion of the urban poor from the benefits of urban life fosters discontent and political unrest. Within the broader context of health and human development, rapid urbanization of poverty and ill health have been characterized as a new human security threat.5 Rapid uncontrolled urbanization results from the interaction between global and local forces. The interconnectedness of cities through trade, business, industry, tourism, international travel, information technology, and media is reshaping social determinants of health that are manifest at the city level. On the other hand, local and national governance capacity in relation to health systems, housing, transport, property rights, migration, land use policy, working conditions, and employment may be unable to cope with the speed of change brought about by global economic restructuring. Inequity in cities that leads to urban poverty, and poor health, therefore, are also products of global and local forces in the urban setting. Public health can play an important role in ameliorating urban poverty through social processes (participation, social capital, social accountability, and social inclusion) that influence urban governance at multiple nodes6 of power. Addressing urban poverty as an urgent public health issue opens a policy space for fairer health opportunities and healthier and more equitable cities.