A hanko (判子), also known as an inkan (印鑑), is a small carved stamp or seal. All adults in Japan own an individual hanko which shows their full name or family name which is used as a way of signing documents or contracts with ink; it is not common to use a signature. ​

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Hanko can be made from various materials like plastic, wood or even ivory. Stone seals have been used in East Asia for thousands of years; similar to wax seals used in Europe, they were a decorative way to seal letters and sign artwork. In the past, their use in Japan was limited to a very few people; the emperor, shoguns, court officials, and other important people would have used seals on official documents. ​

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After the Meiji Restoration in the 19th Century, hanko became part of daily life after a law was passed requiring ordinary people them on important documents. Nowadays, Japanese may have 2 seals: a custom-made one used for formal documents, and another that is used in more casual situations. ​