A dryad is a tree nymph or tree spirit in Greek mythology. The term "dryad" comes from the Greek word "drys," which means "oak". Originally, dryads were considered the nymphs of oak trees specifically, but the term has evolved to refer to tree nymphs in general or human-tree hybrids. Dryads were believed to be supernaturally long-lived and tied to their homes, which were the trees they inhabited. Some dryads, known as hamadryads, were an integral part of their trees, such that if the tree died, the hamadryad associated with it also died. Dryads and the Greek gods punished any mortal who harmed trees without first propitiating the tree-nymphs.

Some of the individual dryads or hamadryads mentioned in Greek mythology include Atlanteia, Phoebe, Chrysopeleia, Dryope, Erato, Eurydice, and Tithorea. Dryads were often depicted as young and beautiful women who took the form of the trees they inhabited. They were not mischievous but rather shy and unassuming.

Dryads have been featured in various works of literature and art, including the fantasy novels of Thomas Burnett Swann. In popular culture, they are often depicted as humanoid-type creatures with insurmountable beauty.