She was portrayed by Patricia Velásquez.
Anck-Su-Nanum was betrothed to the Egyptian king Pharaoh Seti I, but secretly carried out an affair with his high priest, Imhotep. When the pharaoh found out, they both kill him. When the pharaoh's bodyguards approached, she told Imhotep to run while she commited suicide, knowing only he can ressurect her. Imhotep attempted this, going as far as stealing the book of the dead, and nearly succeeded in returning Anck-Su-Nanum's soul to her body, but was stopped before the ritual was complete, and her soul returned to the afterlife.
When Imhotep is revived and regains his power, he sets about reviving Anck-Su-Namun again. He abducts Evelyn Carnahan with the intention of using her as a sacrifice. The ritual is interrupted by the arrival of Rick O'Connell and Evelyn's brother Johnathan. Anck-Su-Namun is revived, but since Evelyn wasn't sacrificed, she is reduced to a reanimated corpse. Anck-Su-Namun is then killed in the ensuing battle by undead soldiers commanded by Jonathan.
The Mummy Returns
10 years later, Anck-Su-Namun is revealed to have reincarnated as a beautiful and cunning thief named Meela Nais. She cons several graverobbers into joining an Egyptian cult that worships Inhotep alongside her and Professor Baltus Hafez who both run the cult together, and helping her exhume Imhotep and resurrecting him. When Evelyn is kidnapped, not for a sacrifice, but purely so that Imhotep can watch her die, Rick (now Evelyn's husband) arrives to save her. In the ensuing chaos, Rick and Evelyn's son Alex is kidnapped, as he hold the location to Ahm Shere and the temple of the Scorpion King in a bracelet on his wrist. To restore Imhotep to his full glory, Anck-Su-Namun tricks her accomplices into opening the cursed chest that would allow him to drain their life forces.
In one flashback, it is revealed that Evelyn is the reincarnation of Nefertiri, the daughter of the same pharaoh to whom Anck-Su-Namun was betrothed and murdered. The two were sparring partners and rivals, their hostility carrying over to their present selves.
Anck-Su-Namun and Imhotep venture throughout Egypt with Alex in tow, determined to find the Scorpion King and gain control of his immortal army. They very nearly succeeded, but are thwarted by Rick and his friends. When the temple of the Scorpion King begins to be sucked into Hell, both Rick and Imhotep are caught hanging from a precipice overlooking the inferno with debris crashing down around them. Rick tells his wife to run, yet she rushes to his aid. Imhotep begs Anck-Su-Namun to save him, yet she flees, leaving him broken-hearted and resinged to the pits of Hell. Anck-Su-Namun is then lost in the temple and swallowed up by a swarm of scarabs, mimicking Beni's death scene in the previous film.
Anck-su-Namun was a cowardly woman who only cared about her beauty. She could never do anything by herself and relied on constant protection.