Pandora opened a pithos, a large storage jar, in the earliest Greek version of her myth.
The word pithos refers to a substantial container used in the ancient Greek world for storing commodities such as grain, oil, or wine. Hesiod’s Works and Days describes Pandora opening this kind of vessel, rather than opening a small hinged box.
The expression “Pandora’s box” became standard because later translators and retellers rendered the Greek vessel as a box or container. The change was influential: modern illustrations usually show a decorated chest, even though a pithos would have looked more like a large jar.
This is one of the best-known translation shifts in classical mythology. Saying “Pandora’s jar” is historically closer to Hesiod’s wording, while “Pandora’s box” is the established English idiom. Both expressions refer to the same mythic event.