Calidris alpina, commonly known as the Dunlin, is primarily found in the coastal regions of the Northern Hemisphere. Its geographical distribution spans across North America, Europe, and Asia. During the breeding season, the Dunlin can be found in Arctic and sub-Arctic regions, including northern Europe (particularly Scandinavia and Iceland), northern Russia, Alaska, and Canada. In the non-breeding season, its range extends to coastal areas worldwide, such as the western and eastern coastlines of the United States, western Europe, the Mediterranean, the Middle East, and parts of Asia including India and Southeast Asia.

The Dunlin typically inhabits coastal wetlands, estuaries, and tidal mudflats during the non-breeding season, where it can find abundant sources of invertebrates to feed on. It favors environments with soft mud or sand that allow for probing and feeding. During the breeding season, Dunlins relocate to Arctic tundra environments characterized by wet fields, mossy areas, and heathlands that offer both nesting sites and food availability.

As a shorebird, the Dunlin plays a crucial role in controlling invertebrate populations within its habitat. It contributes to nutrient cycling and supports the ecological balance within wetland and coastal ecosystems. Its migratory patterns also mean it connects various ecosystems across continents, being a part of larger migratory bird population dynamics. Variations in habitat are evident among its subspecies, which may show adaptations to more specific local conditions such as altitude differences or temperature variations in different parts of its range.