Alfie Evans, the 23-month-old British toddler at the centre of a High Court battle, died on Saturday nearly a week after his life support was withdrawn.
The boy from Merseyside, who had a degenerative brain condition, died at 2.30 a.m., his father Tom Evans said.
On Facebook he wrote: "My gladiator lay down his shield and gained his wings... absolutely heartbroken," the BBC reported.
Alfie's parents lost legal challenges against a High Court ruling allowing the hospital to withdraw ventilation on Monday after being in a semi-vegetative state for more than a year.
Thomas Evans and Kate James's legal campaign attracted widespread media attention and saw them clash with doctors over the Alfie's treatment.
A statement from Alder Hey Children's Hospital in Liverpool, where Alfie was treated, said staff expressed their "heartfelt sympathy", reports the BBC.
More From This Section
Alfie, who was born in May 2016, was first admitted to Alder Hey hospital the following December after suffering seizures, and had been a patient at the hospital ever since.
The parents, who lived in Bootle, wanted to fly the toddler to a hospital in Italy for treatment, but this was rejected by doctors who said continuing treatment was "not in Alfie's best interests".
The court battle between the parents and medical staff lasted for four months.
The couple heavily criticised medical staff, with Thomas Evans suggesting his son was a "prisoner" at the hospital and had been misdiagnosed.
The High Court ruled in favour of hospital bosses on 20 February, after accepting medical evidence that there was "no hope" for Alfie.
Earlier in April, Thomas Evans had visited Pope Francis in Rome, pleading with him to "save our son".
--IANS
ksk/vm