Mommy Fortuna is the tertiary antagonist in the novel and animated movie The Last Unicorn. She is a witch who uses her illusory magic to run the Midnight Carnival, which showcases mythical creatures that are, in truth, just normal animals disguised by her spells. However, her magic only works on weak-minded people who believe whatever comes easiest. She herself appears as the climax of her own show, disguised as Elli, the spirit of old age.
She manages to capture two real mythical creatures for her show; the first is the Harpy Celaeno, the second is the Unicorn of the title. She knows her magic is not strong enough to keep them captive, but she sees these two as her only claim to fame and chooses to keep them even if it means her death.
When the Unicorn is freed by Schmendrick the magician, and frees the Harpy, Mommy Fortuna allows the Harpy to kill her, shouting triumphantly "You never could have freed yourselves alone! I held you!" The Harpy kills her, along with her henchman, Ruhk.
Her magic is weak, and works best with ignorant people. She is just barely powerful enough to contain two real magical creatures, but as Schmendrick says, "The truth melts her magic, always."
In an interview, author Peter S. Beagle described her as "A very 20th century character [...] Nothing matters to her except success in show business terms. [...] She wants to be famous and knows why she isn't - she's not very good. [...] Everyone has dreams, even sloppy old witches."
In the film, she is voiced by Angela Lansbury.