In botany, a stipule is an outgrowth typically borne on both sides of the base of a leafstalk. Stipules are considered part of the anatomy of the leaf of a typical flowering plant, although in many species they may be inconspicuous —or sometimes entirely absent, and the leaf is then termed exstipulate. The word stipule was coined by Linnaeus from Latin stipula, straw, stalk.

In botany, the petiole is the stalk that attaches the leaf blade to the stem. It is able to twist the leaf to face the sun, producing a characteristic foliage arrangement, and also optimizing its exposure to sunlight. Outgrowths appearing on each side of the petiole in some species are called stipules. The terms petiolate and apetiolate are applied respectively to leaves with and without petioles.