Thelocactus macdowellii, called the Chihuahuan snowball, is a species of cactus native to northeastern Mexico.

[2][3] It has gained the Royal Horticultural Society's Award of Garden Merit.

It has 30 or more ribs, each with 5 to 7 millimeter high, conical, rhombic warts at the base.

Endemic to the Mexican states of Coahuila, Nuevo León, and the Chihuahuan Desert, Thelocactus macdowellii grows on scrubland and limestone hills in a very restricted area at an altitude of 1500 meters.

[5] First described as Echinocactus macdowellii in 1894 by Leopold Quehl, with the specific epithet honoring the Mexican gardener and plant collector José Alberto McDowell.