Kieran Maxwell, 13, carried the Olympic flame through Bishop Auckland, County Durham, on June 17, 2012.
During the torch relay, the young amputee — his battle with Ewings Sarcoma, a rare and aggressive form of cancer, cost him his left tibia last March — tripped over his heavy prosthetic leg.
His family had been fundraising to buy the teen a lighter replacement limb from the United States, BBC News reports.
But this week, Britain's biggest lottery winners announced that they're donating the funds necessary to get Kieran a lighter prosthetic leg.
Kieran's mother, Nicola, told the Press Association that her son started "yelling and dancing" when he heard the news.
"He couldn't believe it. I am still pinching myself," she said. "What they have done for Kieran will be a small drop in the ocean for them but for him it will change his life. He can go back to being a normal boy. He can be himself. Words cannot describe what they have done."
The new leg will allow Kieran to walk and run freely without a crutch.
Colin and Chris Wier won £161m ($253 million CAD) in a EuroMillions draw last July. They heard about Kieran's story through the grandmother of one of his friends and decided to give a five-figure donation.
"When we heard about Kieran and his family's fantastic efforts to raise money for a new prosthetic leg, we had to help. It is a privilege to support him," Colin Weir told the Press Association.
At a press conference following news of their lotto win, the Weirs acknowledged that "with great wealth comes great responsibility" and have since been donating large chunks of their fortune to those in need.
"There is still an overwhelming sense of good fortune — we were incredibly lucky and will never forget that," Colin said last month. "But, a year on, the biggest change in our life is that we can now support causes close to our hearts in a more meaningful way. It is a privilege to be in a position to see a situation where help is needed and be able to do something about it."
With financing now secured for Kieran's new leg, Kieran's parents will now fundraise for the Toma Fund, which helps teenagers with cancer.