It's been twenty years since the release of Mariah's record-breaking album The Emancipation of Mimi, which includes mega-hits We Belong Together and It's Like That.
A source said: "Talks have been ongoing for a while and finally everything has fallen into place.
"Mariah was initially set to headline the festival in 2020 and then Covid happened.
"It's part of a series of shows celebrating The Emancipation of Mimi album which had some of her biggest hits on it.
"No doubt it will be a military operation when Mariah arrives in Brighton but the festival can do it before — they pulled off Britney headlining back in 2018."
The musical icon is headlining Brighton Pride for her highly-anticipated return to the UK festival scene.
Mariah Carey will thrill UK crowds for the first time since a sensational series of shows at the Royal Albert Hall in 2019.
In an announcement on Brighton and Hove Pride's social media accounts, Mariah said: "I can't wait to see all of your beautiful faces at Pride on the Park 2025.