Megalomania is a mental disorder causing a person to hold exaggerated opinions about his power or abilities. Someone who thinks he is much more important, powerful, or capable than he really is, despite all evidence to the contrary, would be considered a megalomaniac. The same term would apply to a person who causes harm to himself and others because of an obsession with his power or image. Megalomania has two key components, neither of which applies to God: inaccuracy and injury.
Megalomania involves delusion: what the megalomaniac thinks about himself is not, in fact, true. A megalomaniac is the mediocre chess player who accuses everyone who beats him of cheating, because he’s “too smart” to lose fair and square. Adolf Hitler bungled several decisions during World War II as a result of his megalomania. He refused to listen to the advice of his generals, being far too confident in his own abilities. God is not delusional. God’s self-assessment is true in that He is the only God and He possesses absolute power, sovereignty, and knowledge. So long as God’s claims about Himself are true, He is not expressing megalomania.
A person who believes he is the tallest in a room and refuses to admit otherwise is not a megalomaniac, as long as he actually is taller than anyone else present. The current world record holder in the 100-meter dash is not megalomaniacal for saying he is the “fastest man on earth.” Likewise, when God claims traits such as omnipotence and omniscience, He’s not expressing megalomania—those are His true attributes. It would be fair to say that “megalomania in the biblical God” is a contradiction in terms, since it’s impossible to overstate God’s power and influence.
Megalomania also involves harm. True megalomaniacs hurt themselves and others. Their disconnection from reality results in actions that are irrational, dangerous, or absurd. Consider again the example of Hitler’s over-estimating his own military genius. Or of a movie villain like Darth Vader who kills his subordinates for minor failures. God is not capricious or cruel. God’s actions toward humanity are explicitly intended for our benefit. A deity who submits Himself to humiliation and death as the means to forgive our willful sin is hardly harming us. That God expects us to appreciate and respond to this sacrifice is also not megalomaniacal; it’s common sense.
So, the God of the Bible is not a narcissist or an egomaniac or a megalomaniac. God presents Himself exactly as He is and shows tremendous love and concern for us (Romans 5:8). Neither honesty nor love is characteristic of megalomania.