Li Si (born 280 B. C.，Chu state，central China，died 208 B. C.，Xianyang) was a Chinese statesman who utilized the ruthless but efficient ideas of the political philosophy of Legalism to weld the warring Chinese states of his time into the first centralized Chinese empire，the Qin Dynasty.
In 247 B. C. he entered the state of Qin to begin almost 40 years of service under the ruler later known as Shih Huang-ti (“First Sovereign Emperor").
As minister to the emperor，Li was responsible for most of the radical political and cultural innovations made in Qin after 221 B. C..
Li caused the empire to be divided into 36 regions，each governed by a centrally appointed official.
Under his guidance the emperor standardized coinage and weights and measures and began construction of the Great Wall to keep out barbarians from the north.
Li Si was also influential in creating a unified writing system，which remained substantially the same until recent times.
Finally，in an effort to prevent the growth of subversive thought，Li in 213 B. C. forbade the teaching of history and ordered the “burning of the books，” for which he earned the opprobrium of all future generations of Confucian scholars.
When the emperor died in 209 B. C.，Li became involved in the eunuch Zhao Kao's plot to void the proper succession.
But the two conspirators quarreled，and Zhao Kao had Li executed.