Indus seals are characteristic of a phase of the Indus Civilisation when the first towns were developing (around 2500-1900 BC). They come in a variety of forms, the most typical being a square stamp-seal with a perforated knob on the back and a carved design on the front. The most common design is the unicorn, but there are also script-only designs, geometric designs, a few narrative scenes and a wide variety of other animals.

It is not clear what function Indus stamp seals performed, although they are commonly linked to trade. A number have been found in Mesopotamia, where it is assumed they were taken by merchants from the Indus. However, some scholars believe that the stone from which the seals were manufactured was too soft for everyday use in stamping; they suggest instead that the seals may have been connected with ritual activity, or used to signal social information – such as names and titles. The lugs on the seals indicate they were suspended on a cord and perhaps worn.

The inscriptions on the Indus seals are the oldest writing in South Asia. Because there are no bilingual texts and no records longer than 21 characters, Indus writing remains undeciphered and the language uncertain.