Liu Bang in the context of "Western Han"

The Han dynasty was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD) established by Liu Bang and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–206 BC) and a warring interregnum known as the Chu–Han Contention (206–202 BC), and it was succeeded by the Three Kingdoms period (220–280 AD). The dynasty was briefly interrupted by the Xin dynasty (9–23 AD) established by the usurping regent Wang Mang, and is thus separated into two periods—the Western Han (202 BC – 9 AD) and the Eastern Han (25–220 AD). Spanning over four centuries, the Han dynasty is considered a golden age in Chinese history, and had a permanent impact on Chinese identity in later periods. The majority ethnic group of modern China refer to themselves as the "Han people" or "Han Chinese". The spoken Chinese and written Chinese are referred to respectively as the "Han language" and "Han characters".

The Han emperor was at the pinnacle of Han society and culture. He presided over the Han government but shared power with both the nobility and the appointed ministers who came largely from the scholarly gentry class. The Han Empire was divided into areas directly controlled by the central government called commanderies, as well as a number of semi-autonomous kingdoms. These kingdoms gradually lost all vestiges of their independence, particularly following the Rebellion of the Seven States. From the reign of Emperor Wu (r. 141–87 BC) onward, the Chinese court officially sponsored Confucianism in education and court politics, synthesized with the cosmology of later scholars such as Dong Zhongshu.

The Chu–Han Contention (楚漢相爭), also known as the Chu–Han War (楚漢戰爭), was an interregnum of civil wars in Imperial China between the fall of the Qin dynasty in 206 BCE and the establishment of the Han dynasty in 202 BCE.

After the Qin dynasty was overthrown, the empire was divided into the Eighteen Kingdoms ruled by enfeoffed rebel leaders and surrendered Qin generals according to arrangement by Xiang Yu, the hegemon warlord. Due to dissatisfaction among the rebels, wars and rebellions soon broke out, most prominently between two major powers – Xiang Yu and Liu Bang, who were the rulers of the Western Chu and Han kingdoms, respectively. Other kingdoms also waged war against Chu and Han and among themselves, but these were largely insignificant compared to the Chu-Han conflict. The wars ended with a total victory to Liu Bang at the Battle of Gaixia, during which Xiang Yu committed suicide after losing all his men in a last stand. Having subdued all rival contenders, Liu Bang subsequently proclaimed himself emperor of the newly established Han dynasty.

After Liu Bang defeated Xiang Yu and proclaimed himself emperor of the Han dynasty, he followed the practice of Xiang Yu and enfeoffed many generals, noblemen, and imperial relatives as kings (Chinese: 王; pinyin: wáng), the same title borne by the sovereigns of the Shang and Zhou dynasties and by the rulers of the Warring States. Each king had his own semi-autonomous kingdom. This was a departure from the policy of the Qin dynasty, which divided China into commanderies governed by non-hereditary governors.

The kings were divided into two groups: yìxìng wáng, literally "kings of different surnames", and tóngxìng wáng, literally "kings of the same surname", i.e., the imperial surname Liu. All of the initial kings were yixing wang, with many tongxing wang being created on former territories of removed yixing wang. The yixing wang represented an obvious threat to the Han empire, and Liu Bang and his successors suppressed them as quickly as was practical: they had disappeared by 157 BC. The tongxing wang were originally left to their own devices but, after the Rebellion of the Seven States in 154 BC, their independence was curtailed. Eventually they lost most of their autonomy. For this reason, the title is also translated as "prince" when referring to later kings of the dynasty, to reflect both their link to the ruling house and the vestigial nature of the former vassal kingdoms.

Xiang Yu (c. 232 – c. January 202 BC), born Xiang Ji, was a Chinese warlord who founded and led the short-lived kingdom-state of Western Chu during the interregnum period between the Qin and Han dynasties known as the Chu–Han Contention (206–202 BC). A nobleman of the former state of Chu, Xiang Yu rebelled against the Qin dynasty under the command of his uncle Xiang Liang, and was granted the title of "Duke of Lu" (魯公) by King Huai II of the restoring Chu state in 208 BC. The following year, he led an outnumbered Chu army to victory at the Battle of Julu against the Qin armies led by Zhang Han. After the fall of Qin, Xiang Yu divided the country into a federacy of Eighteen Kingdoms, among which he was self-titled as the "Hegemon-King of Western Chu" (西楚霸王) and ruled a vast region spanning central and eastern China, with Pengcheng as his capital.

Although a formidable warrior and tactician, Xiang Yu was poor in both diplomacy and strategy, especially after dismissing his own adviser Fan Zeng. He was later outcompeted by his main rival Liu Bang during the massive civil war among the rebel kingdoms, which concluded with his eventual defeat and suicide in a last stand at the Battle of Gaixia. The demise of Xiang Yu allowed Liu Bang to subsequently become the founding emperor of the newly established Han dynasty, which is widely regarded as a golden age in Chinese history.