Mammillaria dioica, also called the strawberry cactus, California fishhook cactus, strawberry pincusion or fishhook cactus, is a cactus species of the genus Mammillaria found in California and northwestern Mexico, including Baja California and the state of Sonora.
The plant possesses short, firm tubercles ending in the spines. Most of these spines are whitish and straight, but each tubercle has a longer central spine which is slightly curved and dark.
A single plant can bear both male and female flowers. Some plants may produce bisexual flowers as well, thus totaling three types of flower on a single plant. The flowers are white to cream in color and range from 10 millimeters (0.4 inch) to 30 millimeters (1.2 inches) in length. The fruits produced are bright red and ovoid, often with one end thicker than the other and are edible and tastes like a cross between a strawberry and a kiwi. The seeds are small (0.6 to 0.8 millimeters), black, and pitted.
Polyploid wild plants of this species have been found in Mexico. Both tetraploid and hexaploid varieties have been recorded.
It is sometimes cultivated by gardeners, but requires very well-drained soil.