Sir Elton John, Jennifer Lopez and Stevie Wonder will perform in a live TV special, under the direction of Lady Gaga, to show support for healthcare workers fighting the coronavirus.
The One World: Together At Home event will be broadcast tonight on several US networks and streamed on social media.
More than 100 stars will perform from their homes across the world, to create the two-hour concert.
Gaga and advocacy organisation Global Citizen have already raised $35m (£28m) in seven days for the World Health Organisation’s (WHO) COVID-19 Solidarity Response Fund, according to the singer.
Fans will be able to watch the show live on Instagram,YouTube, Apple, Facebook and Twitter at 1am UK time.
The full show will also be replayed at 7.15pm on Sunday on BBC 1.
During a news conference, Gaga said: “We want to highlight the gravity of this historical, unprecedented cultural movement, and we want to celebrate and encourage the power of the human spirit.”
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She said she plans to raise more money, but explained that the TV special is not a fundraiser: “Put your wallets away, and sit back and enjoy the show you all deserve.”
On its website, the WHO said the event is being put on “in celebration and support of healthcare workers, broadcast to feature real experiences from doctors, nurses and families around the world”.
It will be hosted by US comedians Stephen Colbert, Jimmy Fallon and Jimmy Kimmel as well as some colourful Sesame Street characters.
Other big names include Coldplay’s Chris Martin, David and Victoria Beckham, John Legend, Andrea Bocelli, Celene Dion, Taylor Swift, Alanis Morissette, Keith Urban and Billie Eilish.
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A couple of the One Direction boys are also getting involved too.
Idris Elba and his wife Sabrina – who both tested posted for coronavirus – will also take part.