Ainz Ooal Gown (アインズ・ウール・ゴウン), formerly known as Momonga (モモンガ), is the main protagonist of the Overlord series. He is the guild master of Ainz Ooal Gown, Overlord of the Great Tomb of Nazarick, and the creator of Pandora's Actor. He is regarded as the highest of the Almighty Forty-One Supreme Beings by the NPCs of Nazarick.

A cautious and stingy person, Momonga always tries to plan and control details, avoiding any haphazard actions. Because he doesn't underestimate his opponents, he will usually overkill them. Since being transferred to a new world and becoming an actual Undead being, Momonga could feel himself becoming very cold and calculating, his emotions repressed.

Loyal to his friends and creations, since becoming Lord Ruler of Nazarick in the new world he acts with a certain degree of nobility for his devoted followers. Momonga only does things that will benefit Nazarick or himself, whether it's information or prestige. Although he does have a sense of justice and doesn't hate humans as much as his followers, he holds no attachment to them, and he feels nothing toward their deaths.