What is the standard English phrase for an action that creates many unexpected problems, inspired by Pandora’s jar?

“Opening Pandora’s box” is the standard English phrase for an action that creates many unexpected problems.

The expression comes from the Greek myth in which Pandora opens a container and releases hardships into the human world. In modern English, it usually describes starting a process whose harmful consequences are difficult to predict or control. The phrase can apply to politics, technology, personal decisions, or any situation in which one discovery reveals many complications.

Although the idiom says “box,” the earliest surviving version describes a jar. “Opening Pandora’s box” should also be distinguished from simply making a mistake: the phrase suggests that the action unleashes a chain or collection of troubles. The wording has become common far beyond mythology and is used in everyday journalism and conversation.