Martyn Ashton, 41, from Margam, Neath Port Talbot, had set out to raise about £7,000 for rehabilitation equipment.
Friends suggested he set up a crowd funding page rather than sell his Colnago C59 bike worth £7,000.
He described people's generosity as humbling and touching.
Mr Ashton was a professional stunt cyclist, with his videos Road Bike Party and Road Bike Party 2 gaining more than 28 million views between them on YouTube.
But he lost the use of his legs in an accident during a live show in 2013.
He said equipment for people with disabilities could prove expensive so the money would be put to good use.
"I never, ever thought it would reach £50,000," he said. "I can now think long term. It's a remarkable thing."
A paralysed stunt cyclist has said he can start planning his own long-term care and rehabilitation after receiving £50,000 in donations since starting an appeal four days ago.