"Rainbow" is a song by Sia, released on September 15, 2017, as the lead single from the animated film My Little Pony: The Movie soundtrack. In the film, the song is performed by a pop singer Pegasus pony named Songbird Serenade (voiced by Sia).

The music video for "Rainbow" was released on September 19, 2017. The video was directed by Daniel Askill and features Maddie Ziegler with choreography by Ryan Heffington. The video cuts between footage of Songbird Serenade performing for a packed crowd and Ziegler dancing alone on a stage covered by a thin film of water, wearing a wig resembling Songbird Serenade's mane, and successfully battling and conquering the elements.

"Rainbow" received critical acclaim. Bryan Rolli from Billboard called the song "uplifting", saying "The Australian pop star eschews the vocal acrobatics of past hits like 'Chandelier' in favor of a restrained hook and hypnotic beat, while still sounding as powerful and inspired as ever. She maintains the evenhanded, optimistic spirit that elevates her best songs, singing, 'I can see a rainbow in your tears as the sun comes out.'" Hilary Hughes from MTV said, "'Rainbow' has all the hallmarks of a stellar Sia single: Empowering message, driving beat, and an infectiously catchy melody." Gabriella Ginsberg from Hollywood Life said the song was "simply gorgeous".

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