Harrisia fernowii is a species of cactus found in Cuba.

[1] Harrisia fernowii grows with multi-branched, light green shoots up to 2.5 centimeters in diameter and reaches heights of 2.5 to 3 meters.

The eight to eleven light brown thorns have a darker tip and are up to 6 centimeters long.

The first description by Nathaniel Lord Britton was published in 1909.

[3] The specific epithet fernowii honors American forester Bernhard Eduard Fernow (1851–1923).