Mesembryanthemum crystallinum is a prostrate succulent plant native to Africa, Sinai and southern Europe, and naturalized in the New World. The plant is covered with large, glistening bladder cells or water vesicles, reflected in its common names of common ice plant, crystalline ice plant or ice plant.

Mesembryanthemum is a genus of flowering plants in the family Aizoaceae, indigenous to southern Africa. As with many members of that family, it is characterized by long-lasting flower heads. Flowers of Mesembryanthemum protect their gametes from night-time dews or frosts but open in sunlight. There is an obvious evolutionary advantage to doing this; where sun, dew, frost, wind or predators are likely to damage exposed reproductive organs, closing may be advantageous during times when flowers are unlikely to attract pollinators.