Gymnocalycium oenanthemum is a species of flowering plant in the family Cactaceae, endemic to Argentina.

A slightly flattened sphere growing to 12 cm (4.7 in), it has 10–13 ribs, each containing a row of tubercles with radial spines.

The usually five straight to slightly curved, reddish-gray marginal spines have a darker tip and are up to 1.5 centimeters long.

[2] In cultivation in the UK and other temperate regions it cannot survive freezing, so at least in the winter months it must be kept indoors in a bright, cool environment with minimal watering.

[3][4] Gymnocalycium oenanthemum is widespread in the Argentine provinces of Catamarca and La Rioja at altitudes of 800 to 1300 meters.