Patrick Quinn, whose personal battle with ALS helped power the Ice Bucket Challenge fundraising campaign, died on Sunday at age 37, supporters announced on Facebook.
Mr Quinn was co-founder of the campaign that raised more than $220 million (€186 million) for medical research into amyotrophic lateral sclerosis, more commonly known as Lou Gehrig's Disease, his Facebook page said.
He was diagnosed with ALS on March 8th 2013 and died seven years after his diagnosis, according to his Facebook page.
"It is with great sadness that we must share the passing of Patrick early this morning," his supporters said.
"We will always remember him for his inspiration and courage in his tireless fight against ALS."
Condolences to the Quinn family poured in on social media, with many expressing gratitude for the spotlight he drew to the disease and the need to find a cure.
Viral
The Ice Bucket Challenge went viral on social media in the summer of 2014, when people around the world posted videos and photos of themselves dumping buckets of ice water on their heads and challenged others to do the same while urging donations for ALS research.
Roughly 12,000 to 15,000 Americans may have ALS, according to the US Centres for Disease Control and Prevention.
An estimated five per cent to 10 per cent of ALS cases are believed to be hereditary, but the cause is unknown and there is no cure.
Among Mr Quinn's many honours for raising awareness of ALS and promoting research was a nomination with fellow ALS activist Peter Frates as "Person of the Year" by Time magazine.
Mr Frates died last year at age 34, seven years after his diagnosis.
Mr Quinn was born and grew up in Yonkers, New York.
