Laozi (老子) or Laotzu was the philosopher said to be the author of the Daode jing (道德經), the fundamental text for the religion and philosophy of Daoism; the founder of philosophical Daoism and a deity in religious Daoism and Chinese traditional religions.
We don’t know if he really existed, but there are theories that say that he was teacher to Confucius. That, however, would have placed Laozi in the sixth century (BCE), whereas there exists a first century (BCE) version of the Daode jing.
One theory suggests that the Daode jing is a collection of sayings, compiled over several centuries, and that one of its authors is a teacher referred to naturally as Laozi, meaning ‘Old Master’.
Laozi’s personal name is said to be either Li Er (李耳) or Li Dan (李聃). Claimed by the Tang Dynasty emperors as the founder of their lineage, the sage was granted the title ‘Supremely Mysterious and Primordial Emperor’ or Taishang Xuanyuan Huangdi (太上玄元皇帝).
As a deity and religious personage, Laozi is known as the ‘Supreme Old Lord’ or Taishang Laojun (太上老君) and one of the Three Pure Ones.