In politics, humanitarian aid, and the social sciences, hunger is defined as a condition in which an individual does not have the physical or financial capability to consume sufficient food to meet basic nutritional needs for a sustained period. In the field of hunger relief, the term hunger is used in a sense that surpasses the typical desire for food that all humans experience, also referred to as an appetite. The most severe type of hunger is when malnutrition is widespread, and when people have started dying of starvation through lack of access to sufficient, nutritious food, this results in a declaration of famine.

Throughout history, portions of the world's population have often suffered sustained periods of hunger. In many cases, hunger resulted from food supply disruptions caused by war, plagues, or adverse weather. In the decades following World War II, technological progress and enhanced political cooperation suggested it might be possible to substantially reduce the number of people suffering from hunger. While progress was uneven, by 2015, the threat of extreme hunger had receded for a large portion of the world's population. According to the FAO's 2023 The State of Food Security and Nutrition in the World report, this positive trend had reversed from about 2017, when a gradual rise in number of people suffering from chronic hunger became discernible. In 2020 and 2021, due to the COVID-19 pandemic, there was an increase in the number of people suffering from undernourishment. A recovery occurred in 2022 along with the economic rebound, though the impact on global food markets caused by the invasion of Ukraine meant the reduction in world hunger was limited.

While most of the world's people continue to live in Asia, much of the increase in hunger since 2017 occurred in Africa and South America. The FAO's 2017 report discussed three principal reasons for the recent increase in hunger: climate, conflict, and economic slowdowns. The 2018 edition focused on extreme weather as a primary driver of the increase in hunger, finding rising rates to be especially severe in countries where agricultural systems were most sensitive to extreme weather variations. The 2019 SOFI report found a strong correlation between increases in hunger and countries that had suffered an economic slowdown. The 2020 edition instead looked at the prospects of achieving the hunger related Sustainable Development Goal (SDG). It warned that if nothing was done to counter the adverse trends of the past six years, the number of people suffering from chronic hunger could rise by over 150 million by 2030. The 2023 report reported a sharp jump in hunger caused by the COVID-19 pandemic, which leveled off in 2022. According to the report of United Nations from 2025, hunger has increased globally for 6 years in a row.

Many thousands of organizations are engaged in the field of hunger relief, operating at local, national, regional, or international levels. Some of these organizations are dedicated to hunger relief, while others may work in several different fields. The organizations range from multilateral institutions to national governments, to small local initiatives such as independent soup kitchens. Many participate in umbrella networks that connect thousands of different hunger relief organizations. At the global level, much of the world's hunger relief efforts are coordinated by the UN and geared towards achieving SDG 2 of Zero Hunger by 2030.

There is one globally recognized approach for defining and measuring hunger generally used by those studying or working to relieve hunger as a social problem. This is the United Nation's FAO measurement, which is typically referred to as chronic undernourishment (or in older publications, as 'food deprivation,' 'chronic hunger,' or just plain 'hunger.') For the FAO:

Not all of the organizations in the hunger relief field use the FAO definition of hunger. Some use a broader definition that overlaps more fully with malnutrition. The alternative definitions do however tend to go beyond the commonly understood meaning of hunger as a painful or uncomfortable motivational condition; the desire for food is something that all humans frequently experience, even the most affluent, and is not in itself a social problem.

Very low food supply can be described as "food insecure with hunger." A change in description was made in 2006 at the recommendation of the Committee on National Statistics (National Research Council, 2006) in order to distinguish the physiological state of hunger from indicators of food availability. Food insecure is when food intake of one or more household members was reduced and their eating patterns were disrupted at times during the year because the household lacked money and other resources for food. Food security statistics is measured by using survey data, based on household responses to items about whether the household was able to obtain enough food to meet their needs.

The United Nations publishes an annual report on the state of food security and nutrition across the world. Led by the FAO, the report was joint authored by four other UN agencies: the WFP, IFAD, WHO and UNICEF. The theme of the 2024 report is on how efforts to meet SDG 2.1 & 2.2 can be financed. The FAO's yearly report provides a statistical overview on the prevalence of hunger around the world, and is widely considered the main global reference for tracking hunger. No simple set of statistics can ever fully capture the multi dimensional nature of hunger however. Reasons include that the FAO's key metric for hunger, "undernourishment", is defined solely in terms of dietary energy availability – disregarding micro-nutrients such as vitamins or minerals. Second, the FAO uses the energy requirements for minimum activity levels as a benchmark; many people would not count as hungry by the FAO's measure yet still be eating too little to undertake hard manual labour, which might be the only sort of work available to them. Thirdly, the FAO statistics do not always reflect short-term undernourishment.