In Greek mythology, Pandora opened a pithos, a large storage jar, rather than a box.
Hesiod uses the ancient Greek word pithos for the container. A pithos was a substantial pottery vessel used in the ancient Mediterranean to store commodities such as grain, oil, or wine. Its large size makes “jar” a closer description than the small wooden box often shown in modern illustrations.
The phrase “Pandora's box” arose through later translation and transmission. The Renaissance humanist Erasmus is often credited with popularizing the Latin expression pyxis, meaning box, when translating the Greek story. That wording became deeply established in European languages and popular culture.
The distinction matters because it illustrates how myths change as they move between languages and periods. “Pandora's box” remains the conventional idiom, but pithos is the specific container named in Hesiod's version. Amphora, krater, and kylix are different vessel types and are not the canonical answer here.