Malvella leprosa is a species of flowering plant in the mallow family known by the common names alkali mallow and alkali sida. It is native to much of the western United States, Mexico, Argentina, and Chile. It is known in parts of Australia as an introduced species. In many regions, whether native there or not, the plant is often a noxious weed and easily invades habitat, including areas with alkaline and saline soils. In California, the plant can be found in agricultural lands, including fields and orchards. This is a decumbent perennial herb producing a white-hairy stem up to about 40 centimeters long, spreading along the ground. The leaves are variable in shape but are generally lobed and wavy along the edges, measuring 1 to 3 centimeters wide. Leaves appear in the leaf axils singly or in clusters of up to 3. Each flower is a cup-shaped corolla of five petals up to 1.5 centimeters long in shades of white or light yellow. The disc-shaped fruit is divided into several segments.