The Huangdi Sijing (; lit. "Yellow Emperor's Four Classics") are long-lost Chinese manuscripts that were discovered among the Mawangdui Silk Texts in 1973. Also known as the Huang-Lao boshu (; lit. "Huang-Lao Silk Texts"), they are thought by modern scholars to reflect a lost branch of early syncretist Daoism, referred to as the "Huang–Lao school of thought" named after the legendary Huangdi (黃帝 the "Yellow Emperor") and Laozi (老子 "Master Lao"). One finds in it "technical jargon" derived of Taoism, Legalism, Confucianism and Mohism.
Mawangdui is an archeological site, comprising three Han-era tombs, found near Changsha in modern Hunan Province (ancient state of Chu). In December 1973, archeologists excavating "Tomb Number 3" (dated at 168 BCE) discovered an edifying trove of silk paintings and silk scrolls with manuscripts, charts, and maps. These polymathic texts discussed philosophy, politics, medicine, Daoist neigong, Yin and Yang, and astronomy. Most were unknown in the received literature, ranging from a formulary that modern editors entitled Recipes for Fifty-Two Illnesses and two texts on cauterization – the Zubi Shiyi Mai Jiujing and Yin Yang Shiyi Mai Jiujing, both precursors of the Huangdi Neijing – to the unknown Book of Silk, which lists three centuries of comet sightings.
The Mawangdui manuscripts included two silk copies of the Daodejing, eponymously titled "Laozi". Both add other texts and both reverse the received chapter arrangement, giving the Dejing chapters before the Daojing. The so-called "B Version" included four previously unknown works, each appended with a title and number of characters (字):
Jing Fa (經法 "The Constancy of Laws"), 5000 characters
Shi Da jing (十大經 "The Ten Great Classics"), 4564
Cheng (稱 "Aphorisms"), 1600
Dao Yuan (道原 "On Dao the Fundamental"), 464
Due to textual lacunae, that is gaps in the written text due to the fragmentary preservation of the original ancient silk manuscripts, the original character counts are also uncertain.
The two longest texts are subdivided into sections.