Lao Tse (Chinese 老子, Pinyin Lǎo Zi, also spelled Lao Tzu) is a major figure in Chinese philosophy whose historical existence is debated. Lao Tse is the standard, longstanding spelling if his name in English, but the modern way would be to use Laozi.
Chinese tradition states that he lived in the 6th century BC. Many modern scholars claim that he may have lived in approximately the 4th century BC, during the Hundred Schools of Thought and Warring States Periods. He is credited with writing the seminal Taoist work, the Tao Te Ching (道德經), and became a popular deity in the Taoist religion's pantheon.
In Pinyin it's Lao Zi and the Dao De Jing.
The correct Pinyin spelling is Lao Zi, but this makes me think of 'lousy' so I like the old way better. Whoever decided that z should be pronounced 'ts' is crazy. But I really love 'his' book. ('He' is in quotes because some doubt his very existence. If he is imaginary, where did the book come from?) -- Craig Daniel
172: This discussion is not exactly right. The phoneme "zi"/"tzu" in "Laozi" is pronounced as the English "z" and German "s", not the German "z". Mandarin "c" is homophone with German "z" - for example, "zu Hause" would be pronounced as "cu hao ze". --- Anyway, whether this discussion should be here is dubious, but we can definitely update to the 20th c. spelling of Laozi.
See also The Zen Way to Go.