An anachronism, from the Greek ανά (ana: up, against, back, re-) and χρόνος (chronos: time), is a chronological inconsistency in some arrangement, especially a juxtaposition of person(s), events, objects, or customs from different periods of time. Often the item misplaced in time is an object, but it may be a verbal expression, a technology, a philosophical idea, a musical style, a material, a custom, or anything else associated with a particular period in time so that it is incorrect to place it outside its proper temporal domain.

The intentional use of older, often obsolete cultural artifacts may be regarded as anachronistic. For example, it could be considered anachronistic for a modern-day person to wear a top hat, write with a quill, or carry on a conversation in Latin. Such choices may reflect an eccentricity, or an aesthetic preference.

Another sort of parachronism arises when a work based on a particular era's state of knowledge is read within the context of a later era with a different state of knowledge. Many scientific works that rely on theories that have later been discredited have become anachronistic with the removal of those underpinnings, and works of speculative fiction often find their speculation outstripped by real-world technological development.