Acanthocalycium is a genus of cactus consisting of several species from Argentina, Bolivia, Brazil, Paraguay and Uruguay.

The plants usually remain unbranched or branch slightly from the bases.

Flowers range from yellow to orange or white to pink or magenta and open during the day.

The funnel-shaped flowers, formed by areoles near the apex, have scales on the outside that taper into sharp thorns.

[citation needed] As of October 2023[update], Plants of the World Online accepted the following species:[1]