The Qin Dynasty (Chinese: 秦朝; pinyin: Qín Cháo; Wade–Giles: Ch'in Ch'ao; IPA: [tɕʰǐn tʂʰɑ̌ʊ̯]) was the first imperial dynasty of China, lasting from 221 to 207 BCE. The Qin state derived its name from its heartland of Qin, in modern-day Gansu and Shaanxi. The strength of the Qin state was greatly increased by the legalist reforms of Shang Yang in the 4th century BC, during the Warring States Period. In the mid and late third century BC, the Qin accomplished a series of swift conquests, first ending the powerless Zhou Dynasty, and eventually destroying the remaining six states of the major states to gain control over the whole of China, resulting in a unified China.

During its reign over China, the Qin Dynasty achieved increased trade, improved agriculture, and military security. This was due to the abolition of landowning lords, to whom peasants had formerly held allegiance. The central government now had direct control of the masses, giving it access to a much larger workforce. This allowed for the construction of ambitious projects, such as a wall on the northern border, now known as the Great Wall of China. The Qin Dynasty also introduced several reforms: currency, weights and measures were standardized, and a better system of writing was established. An attempt to purge all traces of the old dynasties led to the infamous burning of books and burying of scholars incident, which has been criticized greatly by subsequent scholars. The Qin's military was also revolutionary in that it used the most recently developed weaponry, transportation, and tactics, though the government was heavy-handed and bureaucratic.

The Emperor of China (Chinese: 皇帝; pinyin: Huángdì, pronounced [xu̯ɑ̌ŋ tî]) refers to any sovereign of Imperial China reigning between the founding of Qin Dynasty of China, united by the King of Qin in 221 BCE, and the fall of Yuan Shikai's Empire of China in 1916. When referred to as the Son of Heaven (Chinese: 天子; pinyin: tiānzǐ, pronounced [ti̯ɛ́n tsɨ̀]), a title that predates the Qin unification, the Emperor was recognized as the ruler of "All under heaven" (i.e., the world). In practice not every Emperor held supreme power, though this was most often the case.^{[citation needed]}

Emperors from the same family are generally classified in historical periods known as Dynasties. Most of China's imperial rulers have commonly been considered members of the Han ethnicity, although recent scholarship tends to be wary of applying current ethnic categories to historical situations. During the Yuan and Qing dynasties China was ruled by ethnic Mongols and Manchus respectively after being conquered by them. The orthodox historical view over the years sees these as non-native dynasties that were sinicized over time, though some more recent scholars argue that the interaction between politics and ethnicity was far more complex. Nevertheless, in both cases these rulers had claimed the Mandate of Heaven to assume the role of traditional emperors in order to rule over China proper.

Zheng Guo or Cheng Kuo (鄭國) was a hydraulic engineer from the ancient Chinese kingdom of Han who designed the Zhengguo Canal in the kingdom of Qin during the Warring States Period. The canal remains to this day, despite having been constructed in the third century BC. The canal was originally designed as a method to trick the ruler of Qin so that Qin could not expand to the east. However, when it was completed, it was a great agricultural boost to the region.