Rumer revealed in her post that she and her boyfriend Derek Richard Thomas had welcomed their little girl via homebirth on 18 April, alongside a photo of the baby peacefully napping on a crocheted blanket.
“You are pure magic,” the new parents wrote, later adding: “You are more than we ever dreamed of.”
Rumer was flooded with love in the comments, getting congratulations from stars like Hilary Duff, Jenna Dewan and Alison Brie.
Her stepmother Emma Hemming Willis was also overjoyed, writing: “Omg we love her so so much.”
Rumer first announced she was expecting with an Instagram post of her bump last December.
At the time, Demi celebrated entering her “hot kooky unhinged grandma era” in a comment.
Louetta is Demi and Bruce Willis’s first grandchild. The stars, who were together from 1987 to 2000, share daughters Rumer, Scout Willis and Tallulah Willis.
Die Hard actor Bruce announced he was taking a step back from acting in March 2022 after being diagnosed with aphasia, a condition which affects the parts of the brain controlling communication.