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
One Love Manchester: Police are expecting up to 130,000 people to attend
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.
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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
8.04pm – 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: The crowd sing along to Ariana's Break Free
One Love Manchester: Niall Horan gives an emotional performance
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: Miley Cyrus says she feels 'honoured' to be performing in Manchester
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".