Stamp seals are a hallmark of the Harappan civilization (2600-1900 BC), the context in which the earliest cities of South Asia emerged. These small stone objects typically have intaglio engravings on the front and raised perforated bosses on the back. Harappans used stamp seals to display and reproduce imagery and writing that played an important role in social interaction. Stamp seals could be used to create impressions in clay, which could then be affixed to containers or doors to control access to goods. As such, Harappan stamp seals were probably essential to establishing and transforming relationships of possession, which would have made them indispensable to the economic activities of corporate groups, people who share common possessions. Stamp seals could have helped distinguish corporate groups, or bind them together in reciprocal relations. Their role in interaction across social boundaries makes stamp seals critical to understanding the Harappan civilization’s political economy.