U+B2E8 Hangul Syllable Dan

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The dan (段) ranking system is used by many Japanese, Okinawan, Korean, and other martial arts organizations to indicate the level of a person's ability within a given system. Used as a ranking system to quantify skill level in a specific domain, it was originally used at a Go school during the Edo period. It is now also used in most modern Japanese fine and martial arts.

Martial arts writer Takao Nakaya claims that this dan system was first applied to martial arts in Japan by Kanō Jigorō (1860–1938), the founder of judo, in 1883, and later introduced to other East Asian countries. In modern Japanese martial arts, holders of dan ranks often wear a black belt; those of higher rank may also wear either red-and-white or red belts depending on the style. Dan ranks are also given for strategic board games such as Go, Japanese chess (shōgi), and renju, as well as for other arts such as the tea ceremony (sadō or chadō), flower arrangement (ikebana), Japanese calligraphy (shodō), and Japanese archery (Kyudo). Today, this ranking system is part of the hallmark, landscape, and cultural "adhesive" of modern Japanese society.

The Chinese character for the word dan (段) literally means step or stage in Japanese, but is also used to refer to one's rank, grade, or station, i.e., one's degree or level of expertise, knowledge and seniority. In Chinese pinyin, however, the same character is pronounced duàn in Mandarin with the 4th tone, and was originally used to mean phase. Dan is often used together with the word kyū (級) in certain ranking systems, with dan being used for the higher ranks and kyū being used for lower ranks.