A woody plant is a plant that uses wood as its structural tissue. These are typically perennial plants whose stems and larger roots are reinforced with wood produced adjacent to the vascular tissues. The main stem, larger branches, and roots of these plants are usually covered by a layer of thickened bark. Woody plants are usually either trees, shrubs, or lianas. Wood is a structural cellular adaptation that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest plants.

A plant with true woody stems contains wood, which is primarily composed of structures made of cellulose and lignin. These structures provide support and a vascular system which woody plants use to move water and nutrients from the roots to the leaves and to move sugars from the leaves to the rest of the plant. Most woody plants form new layers of woody tissue each year, and so increase their stem diameter from year to year, with new wood deposited on both sides of a vascular cambium layer that is present near the outer parts of the stem; under the bark. However, in some monocotyledons such as palms and dracaenas, the wood is formed in bundles scattered through the interior of the trunk..