The expression “open Pandora’s box” means to start a process that releases many unexpected problems.
English speakers use the phrase when an action appears manageable but produces a chain of difficult, harmful, or uncontrollable consequences. It comes directly from the later popular form of the Pandora myth: once the container is opened, troubles escape into the human world and cannot easily be put back.
The expression is related to, but not identical with, “open a can of worms.” Both suggest that an apparently simple action creates complications, yet “open Pandora’s box” specifically invokes the Greek myth and often emphasizes consequences that spread widely. The phrase also preserves the later box version rather than Hesiod’s original jar. In ordinary writing, it can describe political decisions, technical changes, legal disputes, or personal choices without claiming that every result will be evil in a literal mythological sense.