Ohaguro is the name given in Japan to the custom of blackening one's teeth with a solution of iron filings and vinegar. It was especially popular between the Heian and Edo periods, from the 10th century until the late 19th century, but the opening of the country to Western customs during the Meiji period led to its gradual disappearance. It was a tradition practiced mainly by married women and some men, almost always members of the aristocracy and samurai. In addition to Japanese society's preference for black teeth, it was also considered beneficial to health, as it prevented tooth decay by acting as a dental sealant. The practice of dyeing one's teeth black was also a known and widespread practice in southeastern China and Southeast Asia, although with different recipes.

The Heian period is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō. Heian (平安) means 'peace' in Japanese. It is a period in Japanese history when the Chinese influences were in decline and the national culture matured. The Heian period is also considered the peak of the Japanese imperial court, noted for its art, especially poetry and literature. Two syllabaries unique to Japan, katakana and hiragana, emerged during this time. This gave rise to Japan's famous vernacular literature, with many of its texts written by court women who were not as educated in Chinese as their male counterparts.