Duke Huan of Qi (Chinese: 齊桓公; pinyin: Qí Huán Gōng; died 643 BC) was a powerful Hegemon, who rose to be a major regional power from his headquarters in the State of Qi, toward the end of the early phase of the Spring and Autumn period of ancient China, which began after the sack of the Western Zhou capital in BCE 771, and ended with his death. He is listed as one of the "Five Hegemons". His ancestral name was Jiang (姜), clan name Lǚ (呂), and given name Xiǎobái (小白).

Duke Huan was a younger brother of Duke Xiang of Qi, who was murdered by his cousin Wuzhi who usurped the throne. Wuzhi was soon killed himself. Xiaobai's elder brother Prince Jiu, who was in the State of Lu, was supposed to be the heir and had gained support from Duke Zhuang of Lu, and Guan Zhong, who was initially teacher of Jiu, shot an arrow at Xiaobai who was on his way back to Qi from the State of Ju. Xiaobai pretended to be dead and managed to arrive in Qi earlier than Jiu and take the throne after the ministers were persuaded by Bao Shuya. This angered Duke Zhuang of Lu and he started a fight against Qi for Jiu at Qianshi (乾时), but was defeated by Qi troops and even some of his own territory in Wenyang (汶阳) was possessed. Seeing Duke Huan was steady at his throne, Duke Zhuang of Lu killed Jiu in order to make peace. Duke Huan was the Marquis of Qi from 685 BC until his death; under this period the State of Qi reached its zenith, and the Duke himself was elected to be one of the Five Hegemons.

At the start of his reign and on the advice of his trusted retainer Bao Shuya Lord Huan appointed Guan Zhong, an outstanding politician, to be his Prime Minister. Under Guan Zhong's reforms, Qi became the strongest state of the time, allowing Lord Huan to make a greater impact outside his state. Under the slogan of "respecting the king and defending against the barbarian" (尊王攘夷, pinyin: zūnwáng rǎngyí), Lord Huan was recognized the Hegemon by other states. He helped the states of Yan, Xing and Wey against barbarian troops. He also called on some states to attack the state of Chu in order to ‘defend the honor of the king’.

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