Following suicide bomber Salman Abedi's attack at her concert less than two weeks ago, the pop star vowed to return for a benefit gig.
She said she was inspired by the love and compassion on display by the people of Manchester and will be joined by a host of international stars to commemorate those affected.
Ariana will perform at Old Trafford Cricket Ground and police expect some 130,000 people to attend the concert.
One Love Manchester: Ariana will perform at Old Trafford Cricket Ground tonight One Love Manchester: Crowds gather for Ariana Grande benefit gig Sun, June 4, 2017
Crowds gather for the Ariana Grande One Love Manchester benefit gig in tribute of the Manchester terror attack victims.
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Girls wearing Ariana Grande t-shirts waiting to attend the One Love Manchester benefit concert for the victims of the Manchester Arena terror attack
All proceeds from tonight's show will go toward the We Love Manchester Emergency Fund, which was set up to help Manchester's grieving families.
Ariana will headline the concert and will be joined by Justin Bieber, Katy Perry, Miley Cyrus, Coldplay, The Black Eyed Peas, Little Mix, Take That, Robbie Williams, Niall Horan and Pharell Williams.
We will be following all of the action from the show.
See below for all the live updates from tonight's One Love Manchester Concert on BBC.
One Love Manchester: Police are expecting up to 130,000 people to attend
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One Love Manchester: Liam Gallagher has paid tribute to the victims with a heartfelt performance
9.50pm – He jumps into Wall Of Glass. His performance is a poignant one given that he hails from Manchester.
Over the past two weeks he has been singing Oasis track Don't Look Back In Anger to pay tribute to those who were hurt in the attack.
9.45pm – Liam Gallagher has just arrived on stage to play Rock n Roll Star. Will he be joined by his brother later on?
9.44pm – Another surprise for viewers at home is coming up.
One Love Manchester: Justin Bieber breaks down as he pays tribute to the victims
9.32pm – Coldplay are putting on a high-octane performance as they sing Viva La Vida.9.29pm – Ariana has left the stage and Chris is now singing the band's track Fix You, the crowd join in for: "Lights will guide you home and ignite your bones and I will try to fix you."
9.24pm – It's an emotional moment as the crowd wave glow sticks in the air and sing along in defiance.
9.23pm – Coldplay have just walked out on stage with Ariana, they kick off their set with Oasis' Don't Look Back In Anger.
9.19pm – Miley Cyrus tells Nick Grimshaw she wants to be a team with Ariana to help those in need and keep putting on benefit gigs in the future.
9.18pm – Ariana has returned to the stage to sing her hit Love Me Harder.
She tells the audience she will be back with a little surprise for the audience as she rushes to the side of the stage.
9.14pm – Justin breaks down in tears as he pays tribute to those who lost their lives in the horrific attack. He asks the crowd to raise both hands in the air to honour those affected.
9.11pm – He strolls around the front of the stage with his guitar and launches into Cold Water. It's another heartfelt performance.
9.08pm – Justin is next up and before he starts his set with Love Yourself, he tells the crowd: "Evil will never win."
He has chosen to give an acoustic performance of the emotional single and many can be seen wiping away tears as they watch him from the crowd.
One Love Manchester: Katy Perry insists they 'will not be silenced'
9.06pm – Sara reveals they are waiting for Justin Bieber to take to the stage and asks if anyone has seen him.
9.05pm – Sara and Ore are joined by Sally Lindsey and Paddy McGuinness in the studio.
Sally tells the presenters: "We are all coming together to say it's not going to work. This is never going to stop. There's not an ounce of fear out there. The atmosphere is unbelievable. It's such a brilliant idea."
9.00pm – The US singer is giving an emotional performance of Part of Me before insisting "we will not be silenced" and braking into Roar.
8.55pm – Katy Perry has taken to the stage and she takes the opportunity to thank Ariana for organising the show.
She goes on to tell the crowd that "love conquers hate" and asks them to touch the person next to them.
One Love Manchester: Ariana comforts a young girl as she sings with the school choir
8.50pm – Picking up the energy, she launches into Side To Side.
8.48pm – Ariana stands alone on stage and fighting back tears she tells the audience: "I want to thank you all from the bottom of my heart. I love you so so much. I want to thank you for coming to be here and being so strong. I love you all so much.
"I want you to thank you for coming tonight, I love you so much. Thank you.
"I also want to say I had the pleasure of meeting Olivia's mum and as soon as I saw her I started crying and gave her a big hug.
"She told me Olivia would have wanted to hear the hits. So that means that we had a totally different show planned and last night we had to change it."
8.47pm – It's a magical moment as the sun sets over Manchester and the crowd sing along with Miley and Ariana.
8.46pm – The pair dance with one another as they thank their fans for joining them at the benefit gig.
8.44pm – Miley Cyrus has returned to the stage to sing alongside Ariana to perform a duet of Don't Dream It's Over.
8.38pm – The singer and the rapper perform their duet Dang! much to the delight of the crowd.
8.35pm – Ariana's boyfriend Mac Miller has joined her on stage.
One Love Manchester: Ariana fights back tears as she performs with Black Eyed Peas
8.33pm – The camera cuts to the crowd. Many of those watching are wiping away tears as they watch the choir perform.
8.32pm – The 23-year-old has surprised the group by walking out on stage to join them. The choir's lead singer breaks down in tears as Ariana wraps her arms around her shoulders and offers comfort.
8.31pm – Parrs Wood High School Choir can now be seen on stage to single Ariana's single My Everything.
8.30pm – David Beckham sends a video message to those watching at home and at the cricket ground. He says tonight is about remembering those who suffered so much that night but also celebrating their lives.
8.29pm – Ore notes that Imogen's performance was a wonderful opportunity to reflect on the recent events in Manchester.
One Love Manchester: Little Mix start with Wings, which they wrote to empower their fans
One Love Manchester: Ariana performs for the first time following the attack
8.25pm – Taking her place at the piano, the singer starts with her track Hide and Seek. Silence has fallen across the stadium to listen to her stunning vocals.
8.22pm – The singer appears to be fighting back tears as she hugs the band and they declare they will stand as one.
8.18pm – Ariana Grande is now giving an emotional performance of Where Is The Love? with the Black Eyed Peas.
8.14pm – Next up, Ariana returns with Victoria Monet to perform Better Days. They are sit on the steps of the stage to
8.13pm – The girl group have left after just one song – will they return later for a duet?
8.08pm – Little Mix have taken to the stage and they reveal they are starting with Wings as they wrote it to empower their fans.
One Love Manchester: The crowd sing along to Ariana's Break Free
8.04pm – The crowd sing along with the pop star as she chants: "I'm stronger than I've ever been before."
8.01pm – Sporting a One Love Manchester jumper, she starts with an energetic performance of Be Alright before Break Fre
7.57pm – Ariana Grande takes to the stage to perform for the first time following the attack at her concert on May 22.
One Love Manchester: Niall Horan gives an emotional performance
One Love Manchester: Miley Cyrus says she feels 'honoured' to be performing in Manchester
7.56pm – Scooter then reveals he has a message from 15-year-old victim Adam, who is watching from hospital. He reads: "Don't go forward in anger, love spreads." He then tells Adam: "You're our hero tonight."
7.55pm – He goes on to note that he is so proud of those who attended the concert despite the incident on London bridge last night.
7.54pm – Scooter says he is "so grateful" to Ariana for stepping up and helping her fans. He also thanks the Manchester first response team and the bystanders who helped those on the night of the attack.
7.53pm – The organisers of tonight's show, which includes Ariana's manager Scooter Braun, to thank those who helped make the concert possible.
7.52pm – Sara Cox reminds viewers at home that they can donate money to the We Love Manchester Emergency Fund.
7.49pm – The musician has dedicated his next song This Town to his fans and all of those affected by the tragedy in Manchester. He also thanks Ariana for inviting him to perform.
7.45pm – One Direction star Niall Horan has taken to the stage and is starting with his single Slow Hands. The crowd certainly seem happy to see him.
One Love Manchester: Pharrell gets the crow going 'Get Lucky'
7.41pm – The American star launches into a stunning performance of Inspired, which she has dedicated to victims of the Manchester attack and those watching around the world.
7.40pm – Miley is praising Ariana for being a good role model for her fans by organising a benefit concert for those affected by the horrific attack at her gig less than two weeks ago.
7.38pm – Miley is now about to give a solo performance and tells the crowd she feels "honoured" to at the concert. She says their biggest responsibility is to "take care of each other".
7.35pm – Miley Cyrus has joined Pharrell on stage to give an high-octane rendition of his uplifting Happy.
7.34pm – Pharrell tells the crowd: "I don't hear or see or smell fear in this building. All we feel here is love and positivity."
7.32pm – Miley Cyrus and will.i.am can be seen singing and dancing along at the side of the stage.
7.30pm – Pharrell has taken to the stage and asks Manchester to show the world their resilience as he begins to sing his track with Daft Punk, Get Lucky.
7.29pm – Max Beesley chats to Sara and Ore in the studio. He tells them: "[Robbie] did really well. He has a real oneness for Manchester. I met him here about 30 years ago. That was great that he could get through that.
One Love Manchester: Robbie chants 'Manchester, we're strong' along with the crowd
One Love Manchester: Gary Barlow says he feels proud to be performing
7.24pm – The singer is holding back tears and clearly overcome with emotion as he breaks into Angels.
7.17pm – Robbie Williams has now taken to the stage and the crowd are singing along as he chants: "Manchester, we're strong, we're strong."
7.13pm – The trio have moved towards the front of the stage to give a heartfelt performance of Rule The World.
7.08pm – Gary takes a moment to welcome the crowd to the show and he encourages them to sing along to their next track Giants.
7.05pm – Take That have taken to the stage and are giving an energetic performance of their hit single Shine. The crowd are singing along and clapping their hands in a show of unity.
One Love Manchester: Marcus gives a poignant performance of Timshel
7.00pm – Marcus Mumford has taken to the stage and asked the crowd to stand for a minute's silence to remember those who were affected by the tragedy.
He gives a stunning acoustic performance of Mumford & Sons track Timshel. The lyrics are particularly poignant as he sings: "You are not alone in this, we will stand together."
6.59pm – Nick Grimshaw speaks to Take That who are set to perform tonight.
Gary tells him he feels "proud" to be singing, adding: "It's a big night for the north west, the world is watching… people have come and want to have a great night, we want to do our best."
6.58pm – Anita Rani speak to concertgoers who were at Ariana's concert in Manchester less than two weeks ago, with one revealing she felt "nervous" as she arrived at the venue.
6.57pm – The presenters send their condolences to those who were affected in the horrific attack at London Bridge last night.
6.56pm – Sara Cox and Ore Oduba welcome viewers to the One Love Manchester concert. They are sending out a message of "peace, love and unity".