Harrisia tortuosa is a species of cactus in the Trichocereeae tribe.

 Harrisia tortuosa grows as a shrub with upright or later arched or prostrate, dark green shoots that are up to 1 meter long with diameters of 2 to 4 centimeters. There are usually seven rounded, slightly tuberous ribs. The one to three strong central thorns, initially red, later become almost black. They are 3 to 4 centimeters long. The six to ten pale and light-colored marginal spines reach a length of up to 2 centimeters.

The flowers reach a length of up to 16 centimeters. The spherical, bumpy red fruits have a few thorns and reach a diameter of 3 to 4 centimeters.

Distribution: It is native to low altitudes in Uruguay, Paraguay, northeastern Argentina at elevations of 80-300 meters.

Harrisia tortuosa is considered an exotic invasive in Australia.

Taxonomy: The first description as Cereus tortuosus was made in 1838 by Christoph Friedrich Otto and Albert Gottfried Dietrich. The specific epithet tortuosa means ´tortuous, abundant with coils´. Nathaniel Lord Britton and Joseph Nelson Rose placed the species in the genus Harrisia in 1920. Another nomenclature synonym is Eriocereus tortuosus (J.Forbes ex Otto & A.Dietr.) Riccob. (1909).