Many Overlord fans ask, is Momon and Ainz the same person? The answer is yes. Most of the time at least.
In order to join the Adventurer’s guild, Ainz created a fake persona. Momon. He disguises himself by equipping black metal armor with a helmet.
At one point in the series, Momon has a comrade don the armor for him, so that he can appear at the same time as Momon. Ainz did this in order to convince the populace that Momon and Ainz are different people.
This was just a trick though. For 99.9% of the show, Ainz and Momon are the same person.
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Who is Momon in Overlord?

As stated, Momon is Ainz Ooal Gown. They are one in the same.
When Ainz takes on the Momon persona, he does so to go undercover. Momon is characterized by his black armor and two large swords.
He is known worldwide as an adamantium class adventurer. To the commonfolk, he is perceived as one of the few people who could beat Ainz (as they don’t know they are one in the same).
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Who Knows That Momon is Ainz?

Very few people know that Momon is Ainz. This is because Ainz keeps it a secret so he can be undercover as Momon. So far, the only people that know they are the same is Fludar.
Fludar is the strongest wizard in the world (not including Ainz). After learning about Ainz Ooal Gown, he became his servant in order to learn more about sorcery.
Other than Fludar, only the servants of the Nazarick are aware of the connection.
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