Oreocereus hempelianus is a species of cactus native to Peru and Chile.
Oreocereus hempelianus grows with spherical to elongated gray-green shoots that branch from the base and reaches heights of . There are 12 to 24 wide and flat ribs. The initially yellow to reddish spines later become cloudy gray. The one to six central spines are flexible and long. The 10 to 15 radial spines are flexible, spreading and long.
The crooked-edged red flowers appear at the tips of the shoots. They are long. The barrel-shaped fruits reach a length of .[1]
Oreocereus hempelianus is common in the Arequipa region of Peru and Tarapacá, Chile, at altitudes of 2,500 to 3,500 meters.
The first description as Echinopsis hempeliana was made in 1906 by Max Gürke.[2] The specific epithet hempelianus honors the German cactus lover and businessman Georg Hempel.[1] Foreign language common names are "Achacaño" and "Arequipa". David Richard Hunt placed them in the genus Oreocereus in 1987.[3] Nomenclature synonyms are Arequipa hempeliana (Gürke) Oehme (1940), Arequipiopsis hempeliana (Gürke) cross. & Buining (1941) and Borzicactus hempelianus (Gürke) Donald (1970).