An out-of-place artifact (OOPArt) is an artifact of historical, archaeological, or paleontological interest found in an unusual context, which challenges 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.
The term is used in fringe science such as cryptozoology, as well as by proponents of ancient astronaut theories, young Earth creationists, and paranormal enthusiasts. It can describe a wide variety of objects, from anomalies studied by mainstream science to pseudoarchaeology far outside the mainstream to objects that have been shown to be hoaxes or to have mundane explanations.
Critics argue that most purported OOPArts which are not hoaxes are the result of mistaken interpretation and wishful thinking, such as a mistaken belief that a particular culture could not have created an artifact or technology due to a lack of knowledge or materials. In some cases, the uncertainty results from inaccurate descriptions. For example, the cuboid Wolfsegg Iron is not really a perfect cube, nor are the Klerksdorp spheres actual perfect spheres. The Iron pillar of Delhi was said to be “rust proof”, but it has some rust near its base; its relative resistance to corrosion is due to slag inclusions left over from the manufacturing conditions and environmental factors.
Supporters regard OOPArts as evidence that mainstream science is overlooking huge areas of knowledge, either willfully or through ignorance. Many writers or researchers who question conventional views of human history have used purported OOPArts in attempts to bolster their arguments. Creation science often relies on allegedly anomalous finds in the archaeological record to challenge scientific chronologies and models of human evolution. Claimed OOPArts have been used to support religious descriptions of prehistory, ancient astronaut theories, and the notion of vanished civilizations that possessed knowledge or technology more advanced than that known in modern times.