Oleksiak would compete for Canada's swimming team at the Rio 2016 Olympics in five races. Her competition began on day one. In the heats of the 100 m butterfly, she broke the national record and world junior record with a time of 56.73 on her way to the semi-finals. Oleksiak also anchored the final leg of the women's 4×100 m freestyle relay team with Taylor Ruck, Chantal van Landeghem, Sandrine Mainville, and Michelle Williams with the latter only swimming in the heat. In the final of the relay event she held on to the third position against the United States and Australia, winning Canada's first Olympic medal in the women's freestyle relay in 40 years. After the race, the 16-year-old said, "No one really expected this of Canada coming into the meet, but now that we are here, people are going to be surprised at what we do."