The yellow koi (Ogon) is a koi variety with a body that is golden yellow all over; its body color is bright and it is easy to keep.

The yellow koi is a common single-color variety in the koi family. Its whole body is a uniform yellow or golden yellow, and some individuals have scales with a metallic luster that is especially eye-catching in sunlight. Its body shape is similar to that of ordinary koi, its swimming posture is steady, and its temperament is gentle. It is often kept in courtyard fish ponds, park water features, or large aquariums, and is a very popular ornamental fish.

According to differences in body color and luster, koi similar to the yellow koi also include platinum, orange-yellow, and Yamabuki Ogon and other metallic koi varieties; most of them have smooth body surfaces and neatly arranged scales. When selecting a yellow koi, those with pure and uniform body color, no obvious mottling, a well-proportioned head shape, and a balanced body form are generally preferred.

When keeping yellow koi, attention should be paid to keeping the water clean. The fish pond or aquarium should leave enough space for activity and be equipped with a filtration system. Regular water changes can reduce the accumulation of harmful substances. Feeding should mainly use special koi feed. When the water temperature is suitable, they can be fed normally, while in low-temperature seasons the amount of food should be reduced. Common problems of yellow koi are similar to those of other koi. White spot disease and parasitic diseases are more likely to appear when seasons change or water quality is poor. Usually observing the fish's body surface, appetite, and swimming state more often, and isolating and handling them promptly when abnormalities are found, can effectively reduce the risk of disease.

Besides its ornamental value, the yellow koi is also often regarded in folk culture as a symbol of good fortune. Its golden yellow body color implies abundance, so it is favored in courtyard landscaping and feng shui fish ponds.