The National Institute of Horticultural & Herbal Science achieved the breeding of the moon cactus cultivar ‘Hahong’ with dark red color in 2013. Initially, the red dark colored 'Seolhong' and 'Gohong' cultivars were crossed in 2009. Their seeds were harvested after 2 months, sterilized by C2H5OH 70% and NaOCl 2%, and then sowed in 100 mL flasks filled with Kyoto medium + Charcoal 0.1%. The bottom of the germinated shoot was cut, grafted in vitro into a young vine cactus, Hylocereus trigonus, and then planted in a test tube with the same medium. After 6 months, the young grafted cactus was moved into the greenhouse and hardened for 7 days. The cactus was grafted in vivo once a year for four years, the characteristics of growth were surveyed three times from 2011 to 2013, according to the guidelines for the conduct of tests for distinctness, uniformity and stability of Gymnocalycium mihanovichii. ‘Hahong’ has a flat round shape, dark red skin color (R 46B), an average of 8.3 ribs (8 – 10 ribs) similar to ‘Seolhong’. The spine on the body has gray and brown colors and grows up to 4.1 mm in average in a straight shape. The tubercle on the rib is projecting, with a diameter of 39.6 mm, and produces 14.2 offsets in average at 10 months from planting. The preference score for this cactus is 4.2 on a five-point scale. On June 1, 2015, ‘Hahong’ was registered (registration No. 5561) and is now protected by Korean Seed Industry Law.