A tendril is a slender whiplike or threadlike strand, produced usually from the node of a stem, by which a vine or other plant may climb. Its anatomy may be of stem tissue or of leafstalk tissue. Common examples of tendril-producing plants are the grape, members of the squash or melon family (Cucurbitaceae), the sweet pea (Lathyrus odoratus), and the passionflowers (Passiflora (passion-flower) species).

Tendrils are prehensile and sensitive to contact. When stroked lightly on its lower side, the tendril will, in a minute or two, curve toward that side. As it brushes against an object, it turns toward it and—the shape of the object permitting—wraps about it, clinging for as long as the stimulation persists. Later, strong mechanical tissue ( sclerenchyma) develops in the tendrils, thus rendering them strong enough to support the weight of the plant. In addition to their twining character, some tendrils produce terminal enlargements that, on contact with a firm surface, flatten and secrete an adhesive, firmly cementing the tendril to the substrate.