What is the standard English phrase for the mythological container Pandora opened?

Pandora’s box is the standard English phrase for the mythological container Pandora opened.

The expression comes from the Greek myth recorded by Hesiod, but its exact English wording is not ancient. Hesiod described a pithos, a large storage jar. During later Latin transmission, the vessel was associated with a pyxis, a small box or container, helping establish the form that became familiar in European languages.

Today, “to open Pandora’s box” means to begin an action that releases many unforeseen problems. The idiom is used in journalism, politics, law, science, and everyday conversation. It does not necessarily refer to Greek mythology in modern usage.

The phrase is therefore both a mythological label and a metaphor. “Pandora’s jar” is closer to the earliest Greek description, but “Pandora’s box” is the canonical English expression and the form recognized in dictionaries and general reference works.