Introduced by her manager Scooter Braun as "one of the bravest people I know", Grande took the stage and performed her songs "Be Alright" and "Break Free", singing the lyrics "I'm stronger than I've been before" with particular glee.
Ariana's mother Joan, who was instrumental in helping get young fans to safety after the Manchester attack, was also present at the One Love Manchester gig, walking through the crowds and urging fans not to be scared.
The empowering concert flowed with smiles and tears as dedications were made to all those affected by the tragedy.
Millie Robson was among tens of thousands of people to attend Sunday's benefit concert fronted by American singer Ariana Grande.
Take That frontman, Gary Barlow, left the crowd with this message of hope: "We want to stand strong, look at the sky and sing loud and proud". When the show closed, audiences and celebrities alike praised the pop star for her resilience and generosity.
A dancing policeman has become the unlikely star of the One Love Manchester concert and gone viral.
Williams then gave the stage to a video tribute from U2, performing onstage in the USA, with a brief speech from Bono that culminated with him saying, "There is no end to grief, that's how we know there is no end to love".More news: European Union planning to spend tens of billions on climate issues
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The concert raised money for victims and those injured in the suicide bombing that struck at Grande's May 22 show. The concert also came one day after an attack at London Bridge killed seven and injured 48.
Ariana Grande made her triumphant return to Manchester, England - nearly two weeks after a terrorist attack at her concert.
But one moment went viral that had nothing to do with one of the many A-listers who headlined the show.
Bieber shared similar words onstage, even coming close to crying when he spoke about God and those who died at Grande's show.
Revelers dressed for the occasion, with many wearing tops featuring a bee - a symbol for Manchester - and slogans expressing their love for the city.