Megalomania

"Megalomania is a psychopathological disorder characterized by delusional fantasies of power, relevance, or omnipotence. "Megalomania is characterized by an inflated sense of self-esteem and overestimation by persons of their powers and beliefs."Historically it was used as an old name for narcissistic personality disorder prior to the latter's first use by Heinz Kohut in 1968, and is used these days as a non-clinical equivalent. It is not mentioned in the Diagnostic and Statistical Manual of Mental Disorders (DSM) or the International Statistical Classification of Diseases (ICD)." (Wikipedia)