List of emperors of the Han dynasty

The Han dynasty was founded by the peasant rebel leader Liu Bang, known posthumously as Emperor Gao (r. 202–195 BC).

[5] On 11 December 220, Cao's son Pi usurped the throne as Emperor Wen of Wei (r. 220–226 AD) and ended the Han dynasty.

[8] 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.

[13] Use of the era name was formally adopted during the reign of Emperor Wu of Han (r. 141–87 BC), yet its origins can be traced back further.

[15] Since every six-year period was successively marked as yuannian (元年), eryuan (二元), sanyuan (三元), and so forth, this system was considered too cumbersome by the time it reached the fifth cycle wuyuan sannian (五元三年) in 114 BC.

[15] 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.

[16] Since Emperor Wu had just performed the religious feng (封) sacrifice at Mount Taishan, he named the new era yuanfeng (元封).

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.