Zeno was born around 334 BCE in Citium, a city on Cyprus with a mixed Greek and Phoenician population. He came to Athens, by tradition, after being shipwrecked en route to Piraeus with a cargo of Phoenician purple dye. The story has the ring of legend, but his Phoenician origin and his late arrival to philosophy are well-attested. He studied first under Crates the Cynic, then with Stilpo of Megara and Polemo of the Academy, before founding his own school around 300 BCE.
He taught from the Stoa Poikile — the "painted colonnade" on the north side of the Athenian agora — and his followers came to be called Stoikoi, the men of the porch. This is where the philosophy gets its name. The Stoa was a public space; Zeno's teaching was not, like Plato's Academy, set apart from the city. From its origin, Stoicism was a philosophy taught in public, addressed to the citizen, with no requirement of leisure or special initiation.
Zeno's writings have not survived. We know his work through doxographic reports — particularly Diogenes Laertius's Lives Book 7, which preserves a doxographic outline of Stoic doctrine attributed to Zeno and his immediate successors. The system Diogenes summarizes is recognizably the philosophy that would later be taught by Epictetus and lived by Marcus: virtue as the only true good, externals as indifferents, the soul as a fragment of cosmic logos, the goal of living according to nature.
He is reported to have been thin and dark-skinned, of unprepossessing appearance, ascetic in habit, and unusually fond of green figs and sunbathing. He died around 262 BCE, by tradition by his own choice after a fall in old age. His successor was Cleanthes, who held the school for thirty-two years; after Cleanthes, Chrysippus systematized what Zeno had founded.
What Zeno gave the tradition was the architecture — physics, logic, and ethics as one integrated system; the logos as the rational order of the cosmos; the goal of life as alignment with that order; virtue as sufficient for happiness. Almost everything in this codex is a working-out of his initial premise.