Moon Butterfly, also known as Moon the Undaunted, was the 36th Queen of the Kingdom of Mewni, ruling alongside her husband River, is no longer queen of Mewni, the throne having been passed from Star to Eclipsa Butterfly, and much of her memory is in fragments as a result of exposure to the Realm of Magic (though it seems to be fully restored by "Ghost of Butterfly Castle").

As of "Moon Remembers", she and River have left the kingdom to start a new life and formed a community of Mewman refugees.