The 23-month-old kid at the centre of a High Court legal battle, Alfie Evans died, nearly a week after his life support was withdrawn.
Alfie Evans, who was from Merseyside and had a degenerative brain condition, died at 02:30 BST, his father Tom Evans said.
He wrote on his Facebook profile: “My gladiator lay down his shield and gained his wings… absolutely heartbroken.”
The Pope Francis, who took a personal interest in the case, tweeted:
I am deeply moved by the death of little Alfie. Today I pray especially for his parents, as God the Father receives him in his tender embrace.
— Pope Francis (@Pontifex) April 28, 2018
Hundreds of supporters of Alfie’s parents, which are known as Alfie’s Army, released balloons at a park in a tribute to the toddler.
His aunt Sarah Evans thanked the crowd, saying: “Our hearts are broken. We are absolutely shattered as a family.”
Alder Hey Children’s Hospital in Liverpool, where Alfie was treated, gave a statement, saying: staff expressed their “heartfelt sympathy”.
“All of us feel deeply for Alfie, Kate, Tom and his whole family and our thoughts are with them. This has been a devastating journey for them,” it said.
We’re really sorry about the loss of Alfie Evans.