A drey is the nest of a tree squirrel, flying squirrel or ringtail possum. Dreys are usually built of twigs, dry leaves, and grass, and typically assembled in the forks of a tall tree. They are sometimes referred to as "drey nests" to distinguish them from squirrel "cavity nests" (also termed "dens"). In temperate regions, dreys become much more visible in the autumn, when leaf-fall reveals new nests built the previous summer or in early fall.

A favoured site for a drey is a tree crotch about 9–13 m above ground level. Squirrels may also nest in attics or exterior walls of buildings, where a drey may be regarded as a fire hazard, as some squirrels have a habit of gnawing on electrical cables. At other times, squirrels may inhabit a permanent tree den in the hollow of a trunk or large branch.