A nomad is a member of a community without fixed habitation who regularly moves to and from areas. Such groups include hunter-gatherers, pastoral nomads (owning livestock), tinkers and trader nomads. In the twentieth century, the population of nomadic pastoral tribes slowly decreased, reaching an estimated 30–40 million nomads in the world as of 1995.

Nomadic hunting and gathering—following seasonally available wild plants and game—is by far the oldest human subsistence method. Pastoralists raise herds of domesticated livestock, driving or accompanying them in patterns that normally avoid depleting pastures beyond their ability to recover. Nomadism is also a lifestyle adapted to infertile regions such as steppe, tundra, or ice and sand, where mobility is the most efficient strategy for exploiting scarce resources. For example, many groups living in the tundra are reindeer herders and are semi-nomadic, following forage for their animals.

Sometimes also described as "nomadic" are various itinerant populations who move among densely populated areas to offer specialized services (crafts or trades) to their residents—external consultants, for example. These groups are known as "peripatetic nomads".