This article is about the Chinese Qin dynasty (221-207 BC). For smaller Qin empires in the period 350-417 AD, see Early Qin and Later Qin.

The Qin Dynasty (Chinese 秦朝, pinyin Qíncháo, W.-G. Ch'in Ch'ao) was the first dynasty of the Chinese Empire. It arose from the state of Qin, the westernmost of the seven states that vied for supremacy during the period of the Contested Empires. Qin succeeded in conquering all rival empires by 221 BC, uniting all Chinese-populated territory under one crown for the first time. This was the culmination of a development that had already begun in previous centuries, and one of the most important events in China's history. After the unification of the empire, the Qin king Zheng assumed the title of emperor; he is therefore known as Qin Shihuangdi. However, the real architect of the Unified Empire is considered to be its chancellor Li Si. The territory controlled by the Qin dynasty was much larger than that controlled by its predecessors, such as the Shang or Zhou dynasties.

The few years that the Qin dynasty lasted are among the most politically creative periods in Chinese history. Building on the philosophy of legalism, Qin created the basic features of the Chinese state system that endured in the centuries that followed: the imperial bureaucracy, systematic registration of the population and lands for taxation purposes, legitimization of the emperorship, construction of a wall to protect against the peoples of Inner Asia, and the use of uniform measurements, writing, and currency throughout the empire. Last but not least, the name China is derived from the word Qin.

After the death of the first emperor in 210 BC, unrest broke out throughout the country. Despite the Qin's military strength, the ensuing civil war brought down the dynasty. In 207 BC, the rebel Xiang Yu had the third Qin emperor Ziying executed, shortly after which Liu Bang founded the Han dynasty.

For a long time, Chinese historiography unilaterally condemned the Qin dynasty as barbaric and militaristic. Even among Western scholars, the Qin were long considered a typical example of totalitarianism. In recent decades, however, the analysis of archaeological finds has led to a more balanced picture.