Pathological lying, also known as mythomania and pseudologia fantastica, is the chronic behavior of compulsive or habitual lying.
Unlike telling the occasional white lie to avoid hurting someone’s feelings or getting in trouble, a pathological liar seems to lie for no apparent reason. This can make it frustrating or hard to know what to do if you believe you’ve met one.
Though pathological lying has been recognized for more than a century, there’s not yet a clear universal definition of the condition.
Some pathological lying may result from a mental condition, such as antisocial personality disorder (sometimes called sociopathy), while others appear to have no medical reason for the behavior.