megalomania

noun

1. Psychiatry. a symptom of mental illness marked by delusions of greatness, wealth, etc.
2. an obsession with doing extravagant or grand things.

noun

1. a mental illness characterized by delusions of grandeur, power, wealth, etc
2. informal a lust or craving for power

n.“delusions of greatness,” 1866, from French mégalomanie; see megalo- + mania “madness.” n.

1. A psychopathological condition in which delusional fantasies of wealth, power, or omnipotence predominate.
2. An obsession with grandiose or extravagant things or actions.

Delusions of grandeur; an extreme form of egotism. Adolf Hitler is generally considered to have been a megalomaniac.