Ellis Price's mum Laura Pearman held early Christmas Day celebrations at home for her son in Horbury on September 8.
Leeds United got involved and invited Ellis and family for a VIP tour of Elland Road on his Christmas Eve.
Laura wrote on her Facebook page on Sunday (Sept 20) : "At 2:25 this morning, my beautiful baby boy passed in my arms.
"He’s the most precious, brave and courageous person and I’m so proud to have been his mum.
"He was an incredible fighter and left with no pain."
Leeds United tweeted on Sunday: "Fly high Ellis, thank you for sharing your Christmas with us. Yesterday was for you."
Andrea Radrizzani tweeted: "Another little angel left us too soon. RIP Ellis , our prayers for you and your family."
United captain Liam Cooper tweeted: "Our heartfelt condolences go out to Ellis and his family. Fly high little one."
Wellwishers from across the UK sent Ellis thousands of Christmas cards and at least 2,000 presents after a social media appeal went viral.
His grandmother’s garden in Horbury was transformed into a winter wonderland with Santa’s grotto, reindeer, polar bears, penguins and a snow machine on September 8.
On Ellis’s Christmas Eve’ on Monday, Leeds United invited him and his family for a VIP tour of Elland Road.
They went into club owner Andrea Radrizzani’s office and saw the EFL Championship trophy.
Mr Radrizzani and his son spoke to Ellis and his family via FaceTime before Ellis went onto the Elland Road pitch and scored a goal.
The club presented Ellis and his sisters Caitlin, 15 and Alana, 10 with full United kits among other presents.
And former United star Jermaine Beckford arranged for a United shirt signed by Leeds players to be presented to Ellis.
Leeds United star Patrick Bamford sent the shirt he wore during Leeds United's opening Premier League match at Liverpool to Ellis.
Ellis was diagnosed with rare ETMR brain cancer last October.
He underwent two lengthy operations on the cancerous tumour at Leeds Children's Hospital as well as chemotherapy and radiotherapy.
Tragically, Laura was told in July that the cancer has spread and Ellis only had up to six months left to live.
She held early Christmas celebrations with Ellis and his sisters Caitlin and Alana and Ellis's stepdad Ashley Pearman, 33.