The year 2007 marked a critical event in the world history. For the first time, more than half of the world population now lives in cities. In many developing countries, the urbanization process goes along with increasing urban poverty and polluted environment, growing food insecurity and malnutrition, especially for children, pregnant and lactating women; and increasing unemployment. Urban agriculture represents an opportunity for improving food supply, health conditions, local economy, social integration, and environmental sustainability altogether. Urban agriculture is present throughout the world in a diversity of farming systems. Urban dwellers ranging 25-30 % are involved worldwide in the agro-food sector. Urban agriculture will gain in recognition for its benefits and services because urban population and rural-urban migration are increasing. The actual scarcity of knowledge on urban agriculture has somehow hindered the relevance of this activity. Here, we review the social, cultural, technical, economic, environmental, and political factors affecting urban agriculture with examples taken in East Asia, South America, or East Africa. We discuss the definition, benefits, and limitations of urban agriculture. Food security benefit of urban agriculture is evidenced by 100-200 million urban farmers worldwide providing the city markets with fresh horticultural goods. Urban agriculture favors social improvement since the poors spend up to 85 % of their income in food purchase and most urban farmers belong to poorest populations. Sociologically urban farming favors both social inclusion and reduction of gender inequalities, as 65 % of urban farmers are women. Urban agriculture has ecological benefits by reducing the city waste, improving urban biodiversity and air quality, and overall reducing the environmental impact related to both food transport and storage. The production of horticultural goods shows the main benefits of urban agriculture. Fruit and vegetable cro