Diogenes of Sinope was the most famous of the Cynics, a contemporary of Plato and Alexander. Exiled (or fled) from his native city on a charge of "defacing the currency" (παραχάραξις τοῦ νομίσματος), he turned the phrase into a life's programme: to "re-stamp the coinage" of accepted values. At Athens he attached himself to Antisthenes, a pupil of Socrates. He lived in ostentatious poverty — by tradition in a large earthenware jar (πίθος) by the temple of the Mother of the Gods, with a single wallet, staff, and cloak; he threw away even his cup on seeing a boy drink from his cupped hands.

Around him gathered a corpus of chreiai (χρεῖαι) — pointed anecdotes: the request to Alexander to "stand aside, out of my light"; the search for "a human being" with a lamp in broad daylight; the reply, when sold as a slave, that he knew how "to govern men." The principal source is Diogenes Laertius VI 20–81. He is said to have died at Corinth on the day of Alexander's death (323 BCE).

Diogenes authored not a system but a way of life; his "teaching" is a practice. The core:

• Αὐτάρκεια — self-sufficiency: reducing needs to the natural minimum makes one independent of fortune and of other people. Hence the Stoic distinction between the needful and the indifferent.
• Ἄσκησις — bodily-moral training (hardening, voluntary want) as the road to virtue; virtue lies in deeds, not words.
• Κατὰ φύσιν — "to live according to nature," throwing off convention (νόμος, τῦφος — "conceit," empty opinion). A direct ancestor of the Stoic life according to nature.
• Κοσμοπολίτης — asked where he was from, he answered "a citizen of the world" (κοσμοπολίτης) — the first attested use of the word; the source of the Stoic cosmopolis.
• Παρρησία — frank, exposing speech that lays bare the emptiness of status and wealth.

The line of succession Diogenes → Crates → Zeno makes Cynicism a direct root of the Stoa; for Marcus, Diogenes is a model of the sufficiency of virtue and of indifference to externals.

• 08-03 — in the triad of true sages Diogenes, Heraclitus, Socrates, set against the conquerors (Alexander, Gaius, Pompey): they "saw into things, their causes and their matter," and their ruling faculty was true to itself.
• Cynic-Stoic autarkeia — the background of 04-13 (philosophy without tunic, book, or bread) and 04-30 (the philosopher without means); Diogenes is named as the exemplar in the commentary to both.