The traditionally red-headed Ariel now has dark skin, brown eyes and black hair.
19 year-old Halle Bailey, who rose to fame under the wing of pop queen Beyonce said it was a "dream come true" to play the lead role as Ariel in the live-action version of "The Little Mermaid."
Bailey is an R&B singer and was chosen in the rare casting of a black actress for the Disney princess.
She tweeted a cartoon image of the princess in which the traditionally red-headed Ariel has dark skin, brown eyes and black hair.
Director Rob Marshall said Bailey had been cast after an extensive search, and praised her "rare combination of spirit, heart, youth, innocence, and substance -- plus a glorious singing voice."
News of the casting was trending on Twitter late Wednesday, with many fans overjoyed by the decision.
"If your Egyptian adaptations (actually historical) can be white people, Ariel (a fictional character) can be black," wrote one Twitter user, @NiceNurse22.
Like most Disney princesses, Ariel has been portrayed as pale-skinned in previous cartoon films, in which she was voiced by white actress Jodi Benson.
Disney came under criticism last year for "whitewashing" Princess Tiana in cartoon movie "Ralph Breaks the Internet," hastily redrawing the character with darker features just months before the film's release.
Bailey's casting comes more than two decades after Disney cast singer Brandy, who is also black, as Cinderella in a live-action 1997 film.
Bailey is part of Atlanta-based sister duo Chloe x Halle, who received a Grammy nomination for Best New Artist last year.
Beyonce became a mentor of sorts to them after seeing the pair cover her song "Pretty Hurts" in 2013.
They were signed to her label soon after, and Beyonce took them on her tour in 2016.
Former first lady Michelle Obama is a fan of the duo, turned on to their music by daughters Sasha and Malia.
"The Little Mermaid" will be the latest in a crop of live-action remakes of classic Disney movies, including the recent "Aladdin."
Filming is slated to begin next year.
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