The 25-year-old singer quit the British version of "The X Factor" earlier this year to concentrate on her music career, reported Femalefirst.
"Rita is in a dream world as she's landed the ultimate gig. She'll be mixing her two passions of fashion and music and taking over from a TV institution in Tyra," a source said.
"'Next Top Model' bosses wanted to inject some freshness back into the format and they see Rita as the ideal new face. She is releasing a new single later this year to coincide with it," the source added.