Parodia scopa (syn. Notocactus scopa), the silver ball cactus, is a species of flowering plant in the cactus family Cactaceae, native to upland southern Brazil and Uruguay. It is a ball- or cylinder-shaped cactus growing to 5–50 cm (2–20 in) tall by 10 cm (4 in) broad, with a spiny, woolly crown and pale yellow flowers in summer.