Su Qin (?–284 BCE) was a Chinese political consultant and philosopher who was an influential political strategist during the Warring States period. He was born in Chengxuan Village, Luoyang, in present-day Henan Province. According to legend Su Qin was a disciple of Guiguzi, one of the major adherents of the School of Diplomacy. He was the chief advocate of the "Vertical Alliance [wikidata]" (Chinese: 合纵; pinyin: Hézòng, which sought to create an alliance of the other states against the state of Qin. At his most brilliant, Su Qin persuaded the leaders of the six kingdoms of Qi, Chu, Yan, Han, Zhao and Wei to unite against the Qin state through the use of his splendid rhetoric and thereafter wore robes decorated with the insignia of the six states.

The opposing theory, "Horizontal Alliance [wikidata]" (Chinese: 連横; pinyin: Líanhéng) promoted by Zhang Yi, supported bilateral alliances with Qin. The allies of the Vertical Alliance advanced on the State of Qin but were easily defeated due to internal discord between the former enemies. One theory suggests that Su Qin and Zhang Yi mutually reinforced each other's viewpoints in order to achieve their personal goals.^{[citation needed]}

After finishing his studies with Guiguzi, Su Qin travelled for several years and on his return lamented that "My wife doesn't recognize me as her husband, my sister-in-law doesn't recognize me as her brother-in-law, and my parents don't recognize me as their son!". All these misfortunes he blamed on himself and he thereafter shut himself in his room to study. Years later, when Su Qin returned with full honors following his success with the Vertical Alliance system, his family received him with great reverence, causing him to remark on their change of behavior towards him, leading to the rise of another Chinese idiom which means "a change of attitude from arrogance to respect" (Chinese: 前倨後恭).

This period of canvassing is one of the most debated issues in Chinese History. Modern day verification of Su Qin's biography in the Records of the Grand Historian and the Strategems of the Warring States suggests that the content relating to Su Qin in the former work was actually forged by later authors.

At the end of this period of canvassing, Su Qin became chief administrator of the Vertical Alliance and wore the insignia of the six member nations. After he became famous, he returned to his hometown in a blaze of glory. His parents welcomed him thirty li from home, his sister-in-law crawled like a snake whilst the surprise showed on his wife but she dared not look at him, her former stubbornness having become respect. Once more Su Qin lamented "the parents are poor but not the son". Although already an official of the six nation alliance, Marquis Su of Zhao appointed Su Qin ruler of Wu'an in modern-day Henan Province. According to the records of the Vertical Alliance, the Qin State went into decline and would not dare cross the strategic Hangu Pass for a further fifteen years.

The six nation Vertical Alliance started out with each member state pursuing their own interests and as a result the foundations were shallow. A punitive expedition mounted by the State of Qin against the states of Qi, Wei and Zhao brought the end of the Vertical Alliance; Su Qin left the Zhao State and the alliance disintegrated.

The Qi State took advantage of the Yan State and installed a new monarch, King Yi, as well occupying ten cities which the King of Wei asked Su Qin to get back. Su Qin petitioned the King of Qi thus: "The King of Yan is a kinsman of the Qi State and you have snatched his territory. This is bound to draw the elite troops of the Qin State so you must return these cities!"

After the Marquis Wen of Yan died, King Yi ascended the throne. Su Qin had an affair with the late Marquis’ widow and when King Yi learned about the affair, Su Qin, fearing that he might be punished, subsequently left the Yan State and went to Qi where he obtained an important position from King Xuan. When Xuan died, King Min ascended the throne and Su Qin vied with the ministers of state for the monarch's favor. The ministers tried to assassinate Su Qin and he was seriously injured; the Qi king tried to arrest the culprits but failed to do so. On his deathbed Su Qin gave the King a plan to arrest the assassins: after his death, Su Qin was posthumously accused of treason and his body was torn limb from limb in the town square. This prompted Su Qin's would-be assassins to reveal themselves, and they were subsequently executed. Afterwards, Su Qin's spies leaked information to the Qi State provoking the further hatred and anger of the Yan State.