A badger sett or set is a badger's den which usually consists of a network of tunnels and numerous entrances. The largest setts are spacious enough to accommodate 15 or more animals with up to 300 metres (980 ft) of tunnels and as many as 40 openings. Such elaborate setts with extensive tunneling take many years for badgers to complete. Setts are typically excavated in soil that is well drained and easy to dig, such as sand, and situated on sloping ground where there is some cover.
Sett tunnels are usually between 0.5 to 2 metres (1.6 to 6.6 ft) beneath the ground, and they incorporate larger chambers used for sleeping or rearing young. These chambers are lined with dry bedding material such as grass, straw, dead leaves or bracken. Tunnels are wider than they are high, typically around 30 centimetres (12 in) wide by 25 centimetres (9.8 in) high which matches a badger's wide and stocky build.
The material excavated by the badgers forms large heaps on the slope below the sett. Among this material may be found old bedding material, stones with characteristic heavy scratch-marks, and sometimes even the bones of long-dead badgers cleared out by later generations. Most setts have several active entrances, several more which are used rarely, and some which have fallen into disuse.
Setts are not always excavated entirely in soil; sometimes they are made under the shelter of a shed or in a pile of timber or rocks. They may also be excavated using man-made structures like roofs, building foundations, concrete sidewalks, and paved roadways which can lead to damage of such structures including subsidence.
Badger colonies often utilize several setts: a large main sett usually in the central part of a colony's territory and occupied by most of a colony's members as well as one or more smaller outlier setts. Outlier setts may have only two or three entrances and may be used by a small number of colony members when nearby food sources are in season or in autumn when the main sett is crowded with the year's young.
Badgers typically retreat to their setts at daybreak and come out at dusk. In cold regions, setts are dug below the level at which the ground freezes, and all members of the clan sleep in the same chamber, possibly to share body heat.
Sometimes setts or parts of setts that are not being used by badgers are occupied by rabbits or foxes.
In the United Kingdom, badger setts are protected from disturbance or destruction under the Protection of Badgers Act 1992.