An out-of-place artifact (OOPArt or oopart) is an artifact of historical, archaeological, or paleontological interest found in an unusual context, which challenges (or may appear or be purported to challenge) conventional historical chronology by its presence in that context. Such artifacts may appear too advanced for the technology known to have existed at the time, or may suggest human presence at a time before humans are known to have existed. Other examples may suggest contact between different cultures that is hard to account for with conventional historical understanding.