Pathological lying, also known as mythomania and pseudologia fantastica, is a mental disorder in which the person habitually or compulsively lies. The reason for such lies often serves no obvious purpose other than to paint oneself as a hero or victim depending on the circumstance.
It was first described in the medical literature in 1895 by Anton Delbrück. Although it is a controversial topic, pathological lying has been defined as "falsification entirely disproportionate to any discernible end in view, may be extensive and very complicated, and may manifest over a period of years or even a lifetime". A firm concept of the behaviour does not exist, nor any diagnostic criteria that health professionals accept widely; resulting in controversy regarding what it truly means to be a pathological liar. Theories to explain the root causes include stress, an attempt to shift a locus of control to an internal one, and issues relating to low self-esteem.