The emperors of the Han dynasty were the supreme heads of government during the second imperial dynasty of China; the Han dynasty (202 BC220 AD) followed the Qin dynasty (221–206 BC) and preceded the Three Kingdoms (220–265 AD). The era is conventionally periodised into the Western Han (202 BC9 AD) and Eastern Han (25–220 AD).

The Han dynasty was founded by the peasant rebel leader Liu Bang, known posthumously as Emperor Gao (). The longest reigning emperor of the dynasty was Emperor Wu (), who reigned for 54 years. The dynasty was briefly interrupted by the Xin dynasty of the former regent Wang Mang, but he was killed during a rebellion on 6 October 23 AD. The Han dynasty was reestablished by Liu Xiu, known posthumously as Emperor Guangwu () or Guangwu Di, who claimed the throne on 5 August 25 AD. The last Han emperor, Emperor Xian (), was a puppet monarch of Chancellor Cao Cao (155–220 AD), who dominated the court and was made King of Wei. On 11 December 220, Cao's son Pi usurped the throne as Emperor Wen of Wei () and ended the Han dynasty.

The emperor was the supreme head of government. He appointed all of the highest-ranking officials in central, provincial, commandery, and county administrations. He also functioned as a lawgiver, the highest court judge, commander-in-chief of the armed forces, and high priest of the state-sponsored religious cults.

Naming conventions

Emperor

The rulers of the previous Shang () and Zhou (256 BC) dynasties were referred to as 'king' ( ). By the time of the Zhou dynasty, they were also referred to as the Son of Heaven. In 221 BC, King Ying Zheng of Qin completed the conquest of all the Warring States of ancient China. To elevate himself above the Shang and Zhou kings, he accepted the new title of Emperor ( ) and is known to posterity as Qin Shi Huang, the 'First Emperor' of Qin. The new title of emperor was created by combining the titles for the Three Sovereigns and Five Emperors from Chinese mythology. This title was used by each successive ruler of China until the fall of the Qing dynasty in 1911.

Posthumous, temple, and era names From the Shang until the Sui dynasty (581–618) dynasty, Chinese rulers (both kings and emperors) were referred to by their posthumous names in records and historical texts. Temple names, first used during the reign of Emperor Jing of Han (), were used exclusively in later records and historical texts when referring to emperors who reigned during the Tang (618–907), Song (960–1279), and Yuan (1271–1368) dynasties. During the Ming (1368–1644) and Qing (1644–1911) dynasties, a single era name was used for each emperor's reign and became the preferred way to refer to Ming and Qing emperors in historical texts.

Use of the era name was formally adopted during the reign of Emperor Wu of Han (), yet its origins can be traced back further. The oldest method of recording years—which had existed since the Shang—set the first year of a ruler's reign as year one. When an emperor died, the first year of a new reign period would begin. This system was changed by the 4th century BC when the first year of a new reign period did not begin until the first day of the lunar New Year following a ruler's death. When Duke Huiwen of Qin assumed the title of king in 324 BC, he changed the year count of his reign back to the first year. For his newly adopted calendar established in 163 BC, Emperor Wen of Han () also set the year count of his reign back to the beginning.

Since six was considered a lucky number, the emperors Jing and Wu changed the year count of their reigns back to the beginning every six years. Since every six-year period was successively marked as yuannian (), eryuan (), sanyuan (), and so forth, this system was considered too cumbersome by the time it reached the fifth cycle wuyuan sannian () in 114 BC. In that year, a government official suggested that the Han court retrospectively rename every "beginning" with new characters; Emperor Wu accepted this reform in 110 BC. Since Emperor Wu had just performed the religious Feng Shan sacrifice at Mount Taishan, he named the new era yuanfeng (). This event is regarded as the formal establishment of era names in Chinese history. Emperor Wu changed the era name once more when he established the 'Great Beginning' ( Taichu) calendar in 104 BC. From this point until the end of Western Han, the court established a new era name every four years of an emperor's reign. By the Eastern Han, there was no set interval for establishing new era names, which were often introduced for political reasons and celebrating auspicious events.

Regents and empress dowagers

At times, especially when an infant emperor was placed on the throne, a regent, often the empress dowager or one of her male relatives, would assume the duties of the emperor until he reached his majority. Sometimes the empress dowager's faction—the consort clan—was overthrown in a coup d'état. For example, Empress Lü Zhi () was the de facto ruler of the court during the reigns of the child emperors Qianshao () and Houshao (). Her faction was overthrown during the Lü Clan disturbance of 180 BC and Liu Heng was named emperor (posthumously known as Emperor Wen). Before Emperor Wu died in 87 BC, he had invested Huo Guang (), Jin Midi (), and Shangguan Jie (; ) with the power to govern as regents over his successor Emperor Zhao of Han (). Huo Guang and Shangguan Jie were both grandfathers to Empress Shangguan (), wife of Emperor Zhao, while the ethnically-Xiongnu Jin Midi was a former slave who had worked in an imperial stable. After Jin died and Shangguan was executed for treason, Huo Guang was the sole ruling regent. Following his death, the Huo family faction was overthrown by Emperor Xuan of Han (), in revenge for Huo Guang poisoning his wife Empress Xu Pingjun () so that he could marry Huo's daughter Empress Huo Chengjun ().

List of emperors

Below is a complete list of emperors of the Han dynasty, including their personal, posthumous, and era names. Excluded from the list are de facto rulers such as regents and empress dowagers.

+ Western Han (202 BC9 AD) Sovereign Personal name Reigned from Reigned until Posthumous name Temple name Era name YearsThe years of the Chinese lunisolar calendar do not correspond exactly with the years given in the column for era names. Some years given in the table also belong to two reign periods because some era names were adopted before the beginning of the following year. Emperor Gaozu Liu Bang 28 February 202 BC 1 June 195 BCLatin spelling, Chinese characters, and date range come from Emperor Gao Taizu colspan="3" rowspan="4" Emperor Hui Liu Ying 23 June 195 BC 26 September 188 BCLatin spelling, Chinese characters, and date range come from Emperor Xiaohui colspan="2" Emperor Qianshao Liu Gong 19 October 188 BC 15 June 184 BCLatin spelling, Chinese characters, and date range come from colspan="2" colspan="2" Emperor Houshao Liu Hong 15 June 184 BC 14 November 180 BC colspan="2" colspan="2" Emperor Wen Liu Heng 14 November 180 BC 6 July157 BCLatin spelling, Chinese characters, and date range come from . Emperor Xiaowen Taizong Qianyuan 179–164 BC Houyuan 163–156 BC Emperor Jing Liu Qi 14 July157 BC 9 March 141 BC Emperor Xiaojing colspan="2" rowspan="3" Qianyuan 156–150 BC Zhongyuan 149–143 BC Houyuan 143–141 BC Emperor Wu Liu Che 10 March 141 BC 29 March 87 BCLatin spelling, Chinese characters, and date range come from and . Emperor Xiaowu Shizong Jianyuan 141–135 BC Yuanguang 134–129 BC Yuanshuo 128–123 BC Yuanshou 122–117 BC Yuanding 116–111 BC Yuanfeng 110–105 BC Taichu 104–101 BC Tianhan 100–97 BC Taishi 96–93 BC Zhenghe 92–89 BC Houyuan 88–87 BC Emperor Zhao Liu Fuling 30 March 87 BC 5 June 74 BCLatin spelling, Chinese characters, and date range come from . Emperor Xiaozhao colspan="2" rowspan="3" Shiyuan 86–80 BC Yuanfeng 80–75 BC Yuanping 74 BC Marquis of Haihun Liu He 18 July74 BC 14 August 74 BC colspan="2" colspan="2" Yuanping 74 BC Emperor Xuan Liu Bingyi 10 September 74 BC 10 January 49 BC Emperor Xiaoxuan Zhongzong Benshi 73–70 BC Dijie 69–66 BC Yuankang 65–61 BC Shenjue 61–58 BC Wufeng 57–54 BC Ganlu 53–50 BC Huanglong 49 BC Emperor Yuan Liu Shi 29 January 49 BC 8 July 33 BCLatin spelling, Chinese characters, and date range from . Emperor Xiaoyuan Gaozong Chuyuan 48–44 BC Yongguang 43–39 BC Jianzhao 38–34 BC Jingning 33 BC Emperor Cheng Liu Ao 4 August 33 BC 17 April7 BC Emperor Xiaocheng Tongzong Jianshi 32–28 BC Heping 28–25 BC Yangshuo 24–21 BC Hongjia 20–17 BC Yongshi 16–13 BC Yuanyan 12–9 BC Suihe 8–7 BC Emperor Ai Liu Xin 7 May7 BC 15 August 1 BC Emperor Xiao'ai colspan="2" rowspan="2" Jianping 6–3 BC Yuanshou 2–1 BC Emperor Ping Liu Kan 17 October 1 BC 3 February 6 AD Emperor Xiaoping Yuanzong Yuanshi 1–5 AD. While traditional sources do not give an exact date when the Yuanshi era was announced, it was implied that the first year of Yuanshi did not start until the first month of the lunar calendar – i.e., in 1 AD. See, e.g., Ban Gu, Book of Han, vol. 12. Ruzi Ying Liu Ying 17 April6 AD 10 January 9 AD colspan="2" rowspan="2" colspan="2" rowspan="2" Jushe 6–8 AD Chushi 9 AD

+ Continuation of the Han under the Xin dynasty (9–23 AD) Sovereign Personal name Reigned from Reigned until Posthumous name Temple name Era name Years Gengshi Emperor Liu Xuan 11 March 23 AD November 25 ADLatin spelling, Chinese characters, and date range from . King Wushun of Huaiyang Yanzong Gengshi 23–25 AD