Koi (鯉(ã“ã„), RÅmaji: koi, pronounced ) are ornamental domesticated varieties of the common carp Cyprinus carpio, originated from China and widely spread in Japan. They are very closely related to goldfish and, in fact, the style of breeding and ornamentation has become very similar, probably through the efforts of Japanese breeders to emulate goldfish. Koi and tattoos of koi are traditionally considered lucky.