Fox was a distance runner and basketball player for his Port Coquitlam, British Columbia, high school and Simon Fraser University. His right leg was amputated in 1977 after he was diagnosed with osteosarcoma, though he continued to run using an artificial leg. He also played wheelchair basketball in Vancouver, winning three national championships.
In 1980, he began the Marathon of Hope, a cross-country run to raise money for cancer research. Fox hoped to raise one dollar for each of Canada's 24 million people. He began with little fanfare from St. John's, Newfoundland, in April and ran the equivalent of a full marathon every day. Fox had become a national star by the time he reached Ontario; he made numerous public appearances with businessmen, athletes, and politicians in his efforts to raise money. He was forced to end his run outside of Thunder Bay when the cancer spread to his lungs. His hopes of overcoming the disease and completing his marathon ended when he died nine months later.
Fox was the youngest person ever named a Companion of the Order of Canada. He won the 1980 Lou Marsh Award as the nation's top sportsman and was named Canada's Newsmaker of the Year in both 1980 and 1981. Considered a national hero, he has had many buildings, roads and parks named in his honour across the country.