Ariana Grande, Justin Bieber, Coldplay, Katy Perry, Miley Cyrus, Pharrell Williams, Take That, Niall Horan, Little Mix, Robbie Williams, and the Black Eyed Peas will all perform at the concert tomorrow night.
This benefit comes after a terrorist bombing took the lives of 22 people and injured more than 100 at Grande's concert last week in Manchester.
There will also be "additional security checks taking place and everyone will be searched".
He tweeted: 'This means more to us than all the unbelievable things people have done this week. when your daughter asks after her 2nd operation: 'Is Ariana ok?' 'So happy she came I could burst! "This is beyond tragic but we must stand together and not let this break us", Cara Delevingne told her 40 million followers on Instagram alongside a photo that shows what people in these situations must do to stay safe.
Bob Shennan, Director of Radio and Music says: "The One Love Manchester concert on Sunday will be a very special occasion that resonates throughout Manchester, around the United Kingdom and across the globe".
The attacks come less than two weeks after a bomb went off at her concert in Manchester, killing 22 and injuring 59.More news: Three attacks in central London, at least one dead
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All Grande fans who attended the gig on May 22 were offered free passes to Sunday's benefit concert regardless of where they bought their tickets.
Proceeds will go to an emergency fund set up by the city of Manchester and the British Red Cross.
Manchester police said security at both events will include a "significant number of officers from both GMP and colleagues from other forces, some of which will be armed".
"We will not quit or operate in fear".
"Music is meant to heal us, to bring us together, to make us happy". In a statement on Twitter last week, Grande said of the attack: 'We won't let this divide us.
Secondary ticketing sites Seatwave, Get Me In, Viagogo and Stubhub pledged to not allow the resales on their websites, while eBay said it would immediately remove any listings attempting to profit unfairly from the terror attack.
When the benefit concert was officially announced, which is being headlined by Ariana Grande, the BBC was announced as the first official broadcaster of the event.