What does the expression “Pandora’s box” commonly mean in modern English?

The expression “Pandora’s box” commonly means a source of unforeseen troubles. In modern English, opening a Pandora’s box describes starting an action that creates many unexpected and difficult consequences.

The idiom comes from the myth in which Pandora’s container releases evils into the human world. Although the original Greek story describes a jar rather than a box, the later box image became fixed in European languages and popular culture.

The phrase is usually metaphorical rather than literal. Writers apply it to politics, technology, scientific discoveries, legal disputes, and personal decisions when one step appears manageable but produces a chain of complications.

The expression does not simply mean “a dangerous object.” Its key idea is consequence: once the issue is opened or unleashed, controlling everything that follows becomes difficult. That sense is why the phrase remains common far beyond discussions of Greek mythology.