A window box (also called a window flower box or window box planter) is a type of flower container for holding live flowers and plants in the shape of a box that is mounted on or just below the window sill. It can also be used to grow herbs and other edible plants.

Planter boxes are often used for tiny vegetable or herb gardens, for growing flowers in specific areas, or simply for expanding upon the planting space of an area that is difficult to landscape with plants.