Euthanasia is legal in Belgium and the athlete had announced her intentions after the Rio Games in 2016 to follow that path if her condition worsened.
Belgian Paralympic champion Marieke Vervoort has ended her life at age 40 through euthanasia on Tuesday, officials in her hometown of Diest said in a statement.
"Marieke chose euthanasia years ago and gave effect to her choice on Tuesday evening," the statement said.
The athlete had been transparent about her condition and its limitations for years, and was open about how she intended to die if her suffering increased, and that method was assisted dying, which is legal in Belgium.
She announced her intentions after the Rio Games in 2016 to follow that path if her condition worsened.
She said at the time that sport had given her a reason to keep living.
"I'm still enjoying every little moment. When the moment comes when I have more bad days than good days, then I have my euthanasia papers, but the time is not there yet," she told a news conference during the 2016 Paralympic Games.
Vervoort suffered a degenerative muscle disease that caused constant pain, paralysis in her legs and left her barely able to sleep.
She was just 14 years old when diagnosed but Vervoort pursued a sporting life with passion -- playing wheelchair basketball, swimming and racing in triathlons.
She won gold and silver at the 2012 London Games, as well as silver and bronze in Brazil four years later.
But then her eyesight had deteriorated and she suffered from epileptic attacks, and she said that Rio would be her last competition.
"I know when it's enough for me"
Vervoort signed the paperwork to be euthanised back in 2008.
She said in Rio that access to legal assisted dying had given her the courage to continue living for as long as she had, and insisted the practice should not be characterised as "murder".
"It gives a feeling of rest to people," she said then.
"If I hadn't gotten those (euthanasia) papers I think I would already have committed suicide because it's very hard to live with so much pain and suffering and this unsureness.
"I know when it's enough for me, I have those papers."
"We will not forget Marieke Vervoort's great sporting performances, as well as her courage in the face of the disease," said Anne d’Ieteren, President of the Belgian Paralympic Committee.
"Her personality greatly contributed to the immense popularity of Paralympics in Belgium after the 2012 Paralympic Games in London," she added.
The announcement of Vervoort's death sparked an outpouring of reactions on social media.
Former Olympic diving champion Greg Louganis was among those paying tribute to the athlete:
Many Twitter users said Vervoort's story was a powerful case for the right to assisted dying.
Meanwhile, others worried about the impact of the news on disabled people.
"I am bracing for thousands of comments about how it's, of course, completely understandable that a disabled person would kill themselves," said Fiona Robertson, National Equality Convener at the Scottish National Party (SNP).
The city of Diest will host a final farewell ceremony for Vervoort at 6 p.m. CET on October 28.