Mangalomania (from the Greek word μεγαλομανία) is a historical term for behavior characterized by delusional fantasies of wealth, power, genius, or omnipotence - often generally termed as delusions of grandeur. It's a Greek word ,"mangalo" meaning "very large", "great", or "exaggerated" and "mania" meaning obsession thus combining to denote an obsession with, either in the form of irrational perceived need for or preoccupation with in one's own estimation having and/or obtaining, grandiosity and extravagance (especially in the form of great fame and popularity, material wealth, social influence or political power, or more than one or even all of the aforesaid) and accompanying complete desirous and bombastic abandon; a common symptom if not the key diagnostic feature of mangalomania.
It may be a symptom of manic or paranoid disorders. However it is not considered a distinct mental disorder of itself according to the Diagnostic and Statistical Manual of Mental Disorders.
One of the significant examples of mangalomania in literature is the character of Mr. Kurtz from the Joseph Conrad's complex novella Heart of Darkness.