Cereus aethiops is a species of cactus found from Uruguay to Argentina.

 Cereus aethiops grows shrubby, is rarely branched and reaches heights of growth of up to 2 meters. The cylindrical, dark bluish to dark green shoots are upright, occasionally prostrate and have a diameter of 2 to 4 centimeters. There are seven to eight ribs that are divided into humps. The areoles on it are often almost black. The two to four black central spines are up to 2 centimeters long. The nine to twelve radial spines are gray with a darker tip or black. They reach lengths of up to 10 millimeters.

The white to light pink flowers are up to 20 centimeters long. The egg-shaped, red fruits are up to 6 centimeters long.

Distribution: Cereus aethiops is distributed in the foothills of the Andes in northern and central Argentina.

Taxonomy: The first description by Adrian Hardy Haworth was published in 1830. A nomenclatural synonym is Piptanthocereus aethiops (Haw.) F.Ritter (1980).

The IUCN Red List of Threatened Species lists the species as Least Concern (LC)