Every four years, the Summer Olympics celebrate athletes from around the world.
It's all jovial at the opening ceremony, but once the fireworks die down, these athletes are ready to do whatever it takes to win gold.
With the Rio Olympics almost upon us, here are five potential rivalries that could escalate under the Brazilian sun:
Canada vs. U.S.A. (women's soccer)
Pick a sport and it is easy to find a rivalry between Canada and the United States. In the case of women's soccer, the London 2012 Olympics brought it to another level. In the semifinal, Canada led the U.S. 3-2 with 10 minutes left to play, but saw its gold-medal hopes unravel after Norwegian referee Christina Pedersen called a bizarre delay-of-game penalty on the Canadian keeper. The Americans tied the game on the penalty shot, and scored again in extra time on a goal by Alex Morgan. Although Canada rebounded to win the bronze medal in dramatic fashion against France, the Canadian women are ready for revenge against their neighbour to the south. Team Canada kicks off group play on Aug. 3.
Theisen-Eaton vs. Ennis-Hill (heptathlon)
One of the most gruelling events in track and field, the gold-medal fight in heptathlon has two serious contenders. Saskatchewan's Brianne Theisen-Eaton finished 11th at the 2012 Olympics but has shot up the standings over the last four years. At 27, she is the 2016 points leader and defending world indoor champion in pentathlon (five events instead of heptathlon's seven). Standing in her way is the 2012 Olympic gold medallist Jessica Ennis-Hill of Great Britain. The British star is ranked second in points behind the Canadian this year. Look for an intense start to competition on Aug. 12.
Brooke Henderson vs. Lydia Ko (golf)
The two teenage sensations have dominated the golf world in 2016 and the Rio Olympics could be the next chapter to their budding rivalry. Ko, a 19-year-old from New Zealand, is the planet's top-ranked female golfer, but Henderson has been gaining ground recently and is ranked second. She won her first major in June, beating Ko in a sudden-death playoff at the Women's PGA Championship. The teenaged-duo has combined to win the last three LPGA majors. They'll tee off in Rio on Aug. 17.
Phelps has more gold medals (18) than any other Olympian, but he'd have one more if it hadn't been for rival le Clos. The South African stunned the American swimmer in the 200-metre butterfly at the 2012 Games, winning by just 5-100ths of a second and breaking Phelps' streak in individual races. Expect this event to be a major battle when it begins on Aug. 8.