Astrophytum ornatum, the bishop's cap or monk's hood cactus, is a flowering plant of the family Cactaceae, endemic to the Central Plateau of Mexico. It is the largest and tallest species of Astrophytum.

Astrophytum ornatum is endemic in Mexico (from the Guanajuato state to the Hidalgo state), growig in canyons and limestone cliffs. Description: Astrophytum ornatum is a solitary cactus: it grows a globose to shortly columnar stem up to 120 cm high, with a star-shaped cross-section.

Description: Astrophytum ornatumSN|3660]]SN|3660]] is a shortly columnar cactus appearing star-shaped from above, with white cross bands of woolly scales. It appears to be a very variable species especially for the density and distribution of white scales. It is the largest and easiest to grow and also the fastest of the astrophytums.

Astrophytum ornatum is a small cactus with a solitary stem with 5 to 10 straight to spirally arranged ribs lined with clusters of spines. This species is the largest and tallest in the genus. The stem is globular when young but becomes somewhat columnar with age, growing up to 4 feet (1.2 m) tall and 1 foot (30 cm) in diameter.