Harrisia caymanensis is a species of cactus found in the Cayman and Swan Islands.

[1] Harrisia caymanensis grows as a shrub light green shoots, often as long or longer than stem width, to 2.5 cm (1 in) long and 0.5 mm (0.02 in) thick.

The distal areoles often overlapping 6.5 cm (2.6 in) long and 0.7 mm (0.03 in) thick.

The yellowish, ellipsoid to spherical fruits are smooth.

[2] Harrisia caymanensis grow in coastal scrub and scrubby woodland on exposed limestone rock in the Cayman and Swan Islands at elevations of 5–50 metres (16–164 feet).