Zeno of Citium (not to be confused with Zeno of Elea) was the founder of the Stoic school of philosophy.

Zeno was born in 333 BC in the town of Citium. He was brought up as a merchant. At the age of 30 he was shipwrecked near Athens. While in Athens, Zeno asked a shop keeper where men like Socrates could be found. He was told to "Follow that man." It turns out that the man Zeno was told to follow was Crates the Cynic. Zeno became his pupil and later commented "I made a prosperous voyage when I was shipwrecked."

When Zeno began to teach in his own right, he wandered up and down the painted columns known as stoa from which his school of philosophy is named: stoicism.

It is improper to attribute monotheistic ideas to Zeno or any of the other stoics. While their writings may mention "God", it is used interchangeably with "Zeus" and "Nature" or "Reason" (in greek Logos) elsewhere.