The Old Assyrian period (2025 - 1363 BCE) was a pivotal stage in Assyrian history, marking the development of a distinct Assyrian culture, separate from southern Mesopotamia. This era began with the rise of Assur as an independent city-state under Puzur-Ashur I and ended with the foundation of a larger Assyrian territorial state under Ashur-uballit I, transitioning into the Middle Assyrian period.

During most of this period, Assur was a minor city-state, lacking significant political and military influence. The rulers, known as Išši'ak Aššur ("governor of Ashur") instead of šar ("king"), were part of the city's administrative body, the Ālum. Despite its limited political power, Assur was an important economic hub, especially from Erishum I's reign (c. 1974-1935 BCE), known for its extensive trading network extending from the Zagros Mountains to central Anatolia.

The first Assyrian royal dynasty, established by Puzur-Ashur I, ended with the capture of Assur by Amorite conqueror Shamshi-Adad I around 1808 BCE. Shamshi-Adad established the short-lived Kingdom of Upper Mesopotamia, which collapsed after his death in 1776 BCE. Following this, Assur experienced decades of conflict, involving the Old Babylonian Empire, Mari, Eshnunna, and various Assyrian factions. Eventually, under the Adaside dynasty around 1700 BCE, Assur reemerged as an independent city-state. It became a vassal to the Mitanni kingdom around 1430 BCE but later gained independence, transitioning into a larger territorial state under warrior-kings.

Over 22,000 clay tablets from the Old Assyrian trading colony at Kültepe provide insights into the culture, language, and society of this period. The Assyrians practiced slavery, although some 'slaves' might have been free servants due to confusing terminology in texts. Both men and women had similar legal rights, including property inheritance and participation in trade. The chief deity was Ashur, a personification of the city of Assur itself.