In Greek mythology, a jar held Pandora’s gifts and troubles. The familiar English phrase “Pandora’s box” comes from a later translation tradition, but the earliest Greek story describes a large storage jar, or pithos, rather than a box.
The myth appears most fully in Hesiod’s works, especially Works and Days. Zeus sends Pandora to Epimetheus after Prometheus steals fire for humanity. Pandora opens the vessel, releasing illnesses, hardships, and other troubles into the world. Hope remains inside when she closes it again.
The container is often depicted as a small ornate box in paintings, books, films, and popular culture. That image is memorable but does not match the Greek word used by Hesiod. The distinction matters because a pithos was a substantial earthenware storage vessel, commonly used for grain, oil, or wine.
The expression now describes an action that unleashes unforeseen problems, even when the original object is not literally a box.