Harrisia regelii is a species of cactus endemic to Argentina and Uruguay.

Harrisia regelii grows bushy, scrambling, upright, sometimes arched or prostrate, with green stems that have 4-5 tuberculate ribs.

Plants have 1–4 spines, needle-like, initially reddish to almost white thorns later turn gray with a black tip.

The flowers reach a length of up to 9–22 centimeters with reddish hairs on the buds, spineless and pale green sepals.

[1] Plants are found growing from Argentina (Santa Fé, Entre Ríos) to Uruguay.