Euphorbia milii (crown of thorns, Christ plant, Christ thorn) is a species of flowering plant in the spurge family Euphorbiaciae, native to Madagascar. The species name commemorates Baron Milius, once Governor of Réunion, who introduced the species to France in 1821. It is suspected that the species was introduced to the Middle East in ancient times, and legend associates it with the crown of thorns worn by Christ. It is also found in Kerala, India. There is a tale stating that there were Jews living in Kerala and they brought the Christ thorn plant from Israel to India.
It is a succulent climbing shrub growing to 1.8 m (5 ft 11 in) tall, with densely spiny stems. The straight, slender spines, up to 3 cm long, help it scramble over other plants. The leaves are found mainly on new growth, and are obovate, up to 3.5 cm long and 1.5 cm broad. The flowers are small, subtended by a pair of conspicuous petal-like bracts, variably red, pink or white, up to 12 mm broad. The sap is moderately poisonous, and causes irritation on contact with skin or eyes. If ingested, it causes severe stomach pain, irritation of the throat and mouth, and vomiting. The poison contains 5-deoxyingenol. Wat Phrik in Thailand claims to be the home of the world's tallest Christ thorn plant.
This plant has gained the Royal Horticultural Society's Award of Garden Merit.