Extreme poverty is the most severe state of poverty. Many cannot meet basic needs for food, water, shelter, sanitation, and health care. To determine the affected population, the World Bank defines extreme poverty as living on less than USD $1.25 per day (adjusted for PPP). The World Bank estimates that 1.4 billion people currently live under these conditions.

In 1996, the following definition taken from Joseph Wresinski, founder of ATD Fourth World was taken up by the UN Sub-Commission on the Promotion and Protection of Human Rights in s:The Despouy Report on Human Rights and Extreme Poverty.

"The lack of basic security connotes the absence of one or more factors enabling individuals and families to assume basic responsibilities and to enjoy fundamental rights. The situation may become widespread and result in more serious and permanent consequences. The lack of basic security leads to chronic poverty when it simultaneously affects several aspects of people’s lives, when it is prolonged and when it severely compromises people’s chances of regaining their rights and of reassuming their responsibilities in the foreseeable future."

The eradication of extreme poverty and hunger was the first Millennium Development Goal, as set by 179 United Nations Member States in 2000. Economists and activists consider epidemic diseases (AIDS, malaria, tuberculosis) as crucial factors in and consequences of extreme poverty.

Extreme poverty is most common in Sub-Saharan Africa, and South Asia. The proportion of people in extreme poverty fell from 59 to 19 percent during the 20th century and is now the lowest in history.