any North American herb of the family Martyniaceae of the flowering plant order Lamiales, and particularly Proboseidea louisianica. There are nine species of unicorn plants, most having large purple or creamy white flowers.

The unicorn plant is often grown for its novel fruits, which are hanging, hornlike, woody pods with a thick body, 7.6 or 10 cm (3 or 4 inches) long, ending in a curved beak of equal or even greater length. When dry, the beak splits into two clawlike appendages.