Pastoralism is a form of animal husbandry where domesticated animals (known as "livestock") are released onto large vegetated outdoor lands (pastures) for grazing, historically by nomadic people who moved around with their herds. The animal species involved include cattle, camels, goats, yaks, llamas, reindeer, horses, and sheep.

Pastoralism occurs in many variations throughout the world, generally where environmentally effected characteristics such as aridity, poor soils, cold or hot temperatures, and lack of water make crop-growing difficult or impossible. Operating in more extreme environments with more marginal lands means that pastoral communities are very vulnerable to the effects of global warming.

Pastoralism remains a way of life in many geographic areas, including Africa, the Tibetan Plateau, the Eurasian Steppes, the Andes, Patagonia, the Pampas, Australia and many other places. As of 2019^[update], between 200 million and 500 million people globally practiced pastoralism, and 75% of all countries had pastoral communities.

Pastoral communities have different levels of mobility. The enclosure of common lands has led to sedentary pastoralism becoming more common as the hardening of political borders, land tenures, expansion of crop farming, and construction of fences and dedicated agricultural buildings all reduce the ability to move livestock around freely, leading to the rise of pastoral farming on established grazing-zones (sometimes called "ranches"). Sedentary pastoralists may also raise crops and livestock together in the form of mixed farming, for the purpose of diversifying productivity, obtaining manure for organic farming, and improving pasture conditions for their livestock. Mobile pastoralism includes moving herds locally across short distances in search of fresh forage and water (something that can occur daily or even within a few hours); as well as transhumance, where herders routinely move animals between different seasonal pastures across regions; and nomadism, where nomadic pastoralists and their families move with the animals in search for any available grazing-grounds—without much long-term planning. Grazing in woodlands and forests may be referred to as silvopastoralism. Those who practice pastoralism are called "pastoralists".

Pastoralism is a way of turning uncultivated plants like wild grasses into food. In many places, grazing herds on savannas and in woodlands can help maintain the biodiversity of such landscapes and prevent them from evolving into dense shrublands or forests. Grazing and browsing at the appropriate levels often can increase biodiversity in Mediterranean climate regions. Pastoralists shape ecosystems in different ways: some communities use fire to make ecosystems more suitable for grazing and browsing animals.

One theory suggests that pastoralism developed from mixed farming. Bates and Lees proposed that the incorporation of irrigation into farming resulted in specialization. Advantages of mixed farming include reducing risk of failure, spreading labour, and re-utilizing resources. The importance of these advantages and disadvantages to different farmers or farming societies differs according to the sociocultural preferences of the farmers and the biophysical conditions as determined by rainfall, radiation, soil type, and disease. The increased productivity of irrigation agriculture led to an increase in population and an added impact on resources. Bordering areas of land remained in use for animal breeding. This meant that large distances had to be covered by herds to collect sufficient forage. Specialization occurred as a result of the increasing importance of both intensive agriculture and pastoralism. Both agriculture and pastoralism developed alongside each other, with continuous interactions.

A different theory suggests that pastoralism evolved from hunting and gathering. Hunters of wild goats and sheep were knowledgeable about herd mobility and the needs of animals. Such hunters were mobile and followed the herds on their seasonal rounds. Undomesticated herds were chosen to become more controllable for the proto-pastoralist nomadic hunter and gatherer groups by taming and domesticating them. Hunter-gatherers' strategies in the past have been very diverse and contingent upon the local environmental conditions, like those of mixed farmers. Foraging strategies have included hunting or trapping big game and smaller animals, fishing, collecting shellfish or insects, and gathering wild-plant foods such as fruits, seeds, and nuts. These diverse strategies for survival amongst the migratory herds could also provide an evolutionary route towards nomadic pastoralism.^{[citation needed]}

Pastoralism occurs in uncultivated areas. Wild animals eat the forage from the marginal lands and humans survive from milk, blood, and often meat of the herds and often trade by-products like wool and milk for money and food.