They will join pop sensation Mariah Carey at the event in August
The British girl group consists of Mutya Buena, Keisha Buchanan and Siobhan Donaghy. The original line-up reformed in 2011 and have been announced as the second headline act for 2025.
The announcement comes after American mega-star Mariah Carey was revealed as the first headliner for the festival last week.
Pride on the Park, this year's version of the annual Brighton festival, will take place in Preston Park on 2 and 3 August.
The group have had six number one singles in the UK since their first album in 2000 – the second most of any British girl group behind the Spice Girls, along with solo success.
Previous headliners for the festival include Girls Aloud and Mika in 2024 and the Black Eyed Peas and Steps in 2023.
Pre-sale tickets for Pride on the Park 2025 will go on sale on Thursday.
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