Prichard Colon, who suffered a severe brain injury during a 2015 fight, has died aged 33, his father Richard confirmed on social media.
Colon collapsed in his changing room after the fight with Terrell Williams, during which he complained about repeated punches to the back of his head
The Puerto Rican had suffered a brain haemorraghe and after having an operation to reduce brain swelling he was placed in a coma for 221 days.
Colon lived the rest of his life in a vegetative state - unable to walk or talk - and required 24-hour care.
"Good morning, my people. I regret to inform you of the departure of my son Prichard from this earthly world," Richard Colon wrote on Facebook.
"Now he is in a better world. I did everything possible to fulfil his wish, his dream of bringing him on vacation to Puerto Rico as he so desired, but it couldn't be done.
"Thank you for so many years of love and prayers. As much as you can, please keep us in your prayers."
Colon was undefeated in 16 fights with 13 wins by knockout before facing Williams in Fairfax, Virginia.
During the light-middleweight contest, Colon appeared to be struck in the back of the head on several occasions and Williams was deducted a point for illegal blows.
Colon was later docked two points for a low blow and was knocked down in the ninth. Believing the fight was over, Colon's corner team removed his gloves and he was disqualified.
His parents filed a lawsuit seeking more than $50m (£37m) in damages against the ringside doctor and promoters connected with the fight.
That lawsuit remains unsettled.
'A true warrior'
Colon, who was born in Florida but moved to Puerto Rico aged 10, showed great promise as a teenager and won national titles in two weight divisions.
He also boxed at the Brazil pre-Olympics with the aim of winning a spot at the 2012 Games in London, but lost in the quarter-finals and moved into the professional ranks for his debut in 2013.
"A true warrior in every sense of the word, Prichard left us with profound lessons about life, resilience, and our sport," the WBA posted on X.
"Rest in peace, champion."
In 2021, Colon was named an honorary WBC world champion by president of the sanctioning body Mauricio Sulaiman.
"Eleven years of fighting like a true champion receiving the unconditional love from your mother Nieves, your dad and so many friends who cared for Prichard Colon you will never be forgotten," Sulaiman wrote on X.