Oreocereus celsianus, or the old man of the mountain is a member of the family Cactaceae native to the high lands of the Andes in South America, and is named for its fluffy white hair, which may protect it from intense sunlight and extreme temperatures.

Oreocereus celsianus grows with upright, columnar shoots that branch out from the base and reaches heights of up to around 3 metres (10 ft) tall with a diameter of 8 to 12 cm (3.1 to 4.7 in).

O. celsianus is covered in a downy white hair and spines, with greatest density at the tips of stems receding to near-bare at the base.

[3] The first description as Pilocereus celsianus was made in 1850 by Charles Lemaire in Joseph zu Salm-Reifferscheidt-Dyck's Cacteae in horto Dyckensi cultae anno 1849.

[5] Oreocereus celsianus occurs in the Bolivian departments of Chuquisaca, Potosí and Tarija, Peru, and the Argentine province of Jujuy in the puna vegetation at altitudes of 2900 to 3600 meters.