Percy Alfred Williams (May 19, 1908 – November 29, 1982) was a Canadian athlete, winner of the 100 and 200 metres races at the 1928 Summer Olympics and a former world record holder for the 100 metres sprint.

Williams was the only child of Frederick Williams, who was originally from England, and Charlotte Rhodes, who hailed from St. John's, Newfoundland. At the age of 15, Williams suffered from rheumatic fever and was advised to avoid strenuous physical activities. However, as his high school required participation in athletic competitions, he started training in sprint in 1924 and by 1927 became a local champion.

At the 1928 Olympic trials, Williams won the 100 and 200 metres races, equaling the Olympic 100 metres record of 10.6 seconds.

To earn his travel ticket for the trials, Williams and his volunteer coach, Bob Granger, worked as waiters and dishwashers in a railroad dining car, and Vancouver track fans raised the money to pay Granger's transatlantic ship passage to the 1928 Olympics.

In the second round of the 100 metres at Amsterdam, Williams again equaled the Olympic record with a time of 10.6 seconds and did the same in his semi-final, but placed second to Bob McAllister. The final opened with two false starts, first by Wilfred Legg and then one by Frank Wykoff. Williams took the lead off the start and never relinquished it, winning the gold over Jack London with Georg Lammers third. Williams then won the 200 metres two days later, coming from behind to overtake Helmut Körnig, who had led out of the bend. It was Williams' eighth race in four days and he was the first non-American to complete the sprint double. Williams was also part of the Canadian team which was disqualified in the final of the 4 × 100 metre relay contest.

Williams's victories were front-page news in Canada and he returned a national hero, feted by enormous crowds across the country. An estimated 25,000 people turned out to welcome him at the Canadian Pacific Railway station at the foot of Granville Street in Vancouver. Williams was met off the train by Mayor L. D. Taylor and Premier Simon Fraser Tolmie. They bundled him and Granger into cars and paraded them through the confetti-filled city. The event was broadcast live by reporters with microphones stationed along the route.

Williams showed that his success was not an accident, setting a World Record at the Canadian Track and Field Championships at Varsity Stadium in Toronto in 1930. He then won the 100 yard dash at the inaugural British Empire Games (now known as the Commonwealth Games) in Hamilton, Ontario, but tore the tendons in his upper left leg around the 70 yard mark and never made a full comeback. At the 1932 Summer Olympics in Los Angeles, he was eliminated in the semi-finals of the 100 metre event. With the Canadian team he finished fourth in the 4 × 100 metre relay competition. Subsequently, Williams stopped running and became an insurance agent.

In August 1940, Williams joined the Non-Permanent Active Militia, his occupation listed as "Salesman" and religion as "C of E" (Church of England). He also served as a civilian pilot during World War II, ferrying aircraft around the country for Canadian Airways, then became a civilian flight instructor with the Royal Canadian Air Force.