A Dan rank is a Japanese mark of competence. It is awarded to students of martial arts, based on their competence and skill levels. Interestingly, the Dan rank is not limited to martial arts alone. In Japan, Dan ranks are awarded in the field of Ikebana and tea ceremony too. But here too, they signify the highest level of achievement.

Some of the martial arts where Dan ranks are awarded are Karate, Aikido, Judi, Jiu-Jitsu and certain sword arts. The term Dan first appears to have been used in martial arts by Jigoro Kano, the founder of Judo. He awarded Shodan, the lowest Dan rank, to two of his senior students. Today, almost all Dan rankers wear black belts, which have somehow come to mean a high level of expertise.

There are several degrees in Dan, the most common being the first to the fifth. The degrees go all the way up to ten. Higher Dan degrees are very difficult to attain, and require years of practice and commitment.

The Dan grades can be awarded by higher grade holders, steering committees or the principal dojo. So there is no achievement level that is universal. It varies from school to school; even the yardsticks can be different. In fact, Dan ranks do not necessarily warrant a black belt. Some styles do not use a black belt to indicate an advanced rank.

The highest Dan ranks are sometimes given to the founders of schools or leaders of a style and they alone have the right to bestow it on other students. This system of evaluation has led to the disappearance of higher ranks from some orders. There are some styles where a Dan rank is not considered to be the highest achievement. An instructor or judges certificate is seen as more worthy.

Broadly, the Dan ranks can be classified as:

- Shodan: first degree black belt
- Nidan: second degree black belt
- Sandan: third degree black belt
- Yondan (or yodan): fourth degree black belt
- Godan: fifth degree black belt
- Rokudan: sixth degree black belt
- Nanadan (or shichidan or sichidan): seventh degree black belt
- Hachidan: eighth degree black belt
- Kudan (or kyudan): ninth degree black belt
- Judan: tenth degree black belt

The lower ranks stand for physical abilities and knowledge. The higher Dan ranks are usually given on the basis of leadership abilities and teaching skills. The highest rank holders are those who have the potential to be masters and the torchbearers of the art form.