Marmots are found north of Mexico and in Eurasia from the European Alps through north-central Asia, the Himalayas, and northeastern Siberia to the Kamchatka Peninsula. They inhabit open country in mountains and plains, preferring montane meadows, steppes, tundra, and forest edges. All live in burrows that they excavate, and most mountain species construct burrows beneath boulder fields, rocky slopes, and crevices in cliff faces. This terrain provides protection from predators such as grizzly bears, which are aggressive diggers and a significant predator of the Alaska marmot (Marmota broweri) in the Brooks Range. Rocks and cliffs also serve as observation sites where the rodents sit upright watching for both terrestrial and aerial predators. When alarmed, marmots emit a sharp, piercing whistle and scurry to their burrows if danger persists.

Marmots are active during the day (diurnal) and are almost entirely vegetarian. The Alaska marmot, which grazes on low-nutrient tundra vegetation, must seek productive foraging areas where it competes indirectly with other mammalian grazers, including caribou, Dall's sheep (bighorn sheep), and voles (vole). Some marmots, such as the Alpine marmot (M. marmota) and the hoary marmot (M. caligata) of northwestern North America, are gregarious and social, but others, including the woodchuck (M. monax) of Canada and the United States, are solitary. All hibernate (hibernation) in winter, most of them deeply, although some may emerge from their burrows for short periods on mild winter days. During hibernation they live on fat reserves accumulated during the summer. The hoary marmot hibernates for up to nine months, its fat reserves amounting to 20 percent of its total body weight. Marmots mate soon after they emerge from hibernation. Gestation lasts about a month, and a litter of generally 4 or 5 (recorded extremes range from 2 to 11) is born in a nest within the burrow. Most marmots produce young every year, but the Olympic marmot (M. olympus) of the Olympic Mountains in the United States bears young every other year.

Marmots belong to the squirrel family (Sciuridae) within the order Rodentia (rodent). The closest living relatives of marmots are ground squirrels (ground squirrel) and prairie dogs (prairie dog). Marmots' evolutionary history is recorded in North America by fossils of extinct species from the Late Miocene Epoch (11.2 million to 5.3 million years ago). In Eurasia there is no evidence earlier than the Pleistocene Epoch (1,800,000 to 10,000 years ago).