Kasabian, from Parson Cross, was diagnosed with cancer when he was two years old but developed inoperable brain tumours last year.
The passing of Kasabian, whose fight against cancer won him widespread admiration, was confirmed yesterday morning on Twitter by his dad, Simon who wrote: "Kas passed peacefully in his sleep."
Since then, hundreds of people have paid tribute to the brave Sheffield United fan.
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Blades' striker Billy Sharp wrote on Twitter: "So sorry and sad to hear the news of the passing of Kasabian this morning,u have touched the hearts of millions,so happy I got to meet u"
Last month Billy Sharp dedicated United's win against Chesterfield and the goal he scored to little Kas, as part of the #1LastSmile4Kasabian campaign on Twitter.
Sharp and Blades teammate Chris Basham visited Kasabian last month, and Sharp enlisted the help of former Southampton teammate Adam Lallana to make one of Kasabian's dreams come true - to receive a video message from England skipper Wayne Rooney.
Rooney sent Kasabian his signed shirt from last month's Scotland game, and Sharp - named man of the match as United beat Chesterfield - dedicated the victory to Kasabian in his live post match interview with Sky Sports.
The Sheffield United official account Tweeted yesterday: "Sorry to learn that young Blade Kasabian has passed away.
"We propose a minute’s applause on 8mins for the 8yo at today’s game #twitterblades"
Sheffield United fans also remembered Kasabian's life with a round of applause during the eighth minute of yesterday's game.
Scores more people have also paid tribute to Kasabian on social media.
Tammy Brown said: "Rip to the most amazing little boy I have ever know u did us all proud we love u so much sending big hugs and kisses right ur way."
Lippy Lisa Marie said: "You will never be forgotten dude.
"Such a warrior and a soldier to go through what you did. Many of people are truly heartbroken over your passing today.
"You was known by the world, you touched people's hearts, we all love you. Good night, God bless, Fly safe beautiful boy."
Claire Nundy said: "RIP Kasabian. You touched the hearts of many.
"Fly high with the angels and show them your footballing skills. Our thoughts and condolences to his family and friends from all at Killamarsh Dynamos."
Issy Menzies said: "Sweet dreams lil man, I've followed your story n am heartbroken to hear to you have lost your battle.
"My heart goes out to your family. Your memory will always live on handsome. Fly high lil man always loved n never forgotten"
Margaret Wood said: "R.I.P Kasabian you're were such a brave boy God has another special Angel in his Garden thoughts are with his family and friends at this sad time."
Laura Dobson said: "Good night & God bless little man. A true warrior, you touched so many people's hearts. RIP kasabian."
Tracy Thompson said: "R.I.P kasabian thinking of all his family and friends at this very sad time."
Lisa Chambers-fry said: "R.I.P. to such a brave little boy. God bless you Kasabian..fly free with angels."
When Kasabian was told his cancer had returned this June he responded by starting a massive fundraising campaign to build a new clinic at Sheffield Children’s Hospital.
The selfless youngster even tried to give his wish from the Make-A-Wish Foundation away to another youngster who he thought deserved it.