After a thrilling but weather-disrupted first full day of sporting action on Saturday, day two of the Olympics will see 13 gold medals up for grabs in sports ranging from archery to skateboarding.
But all eyes will be on the battle for gold in the swimming pool at La Defense Arena, where Britain's Adam Peaty faces a duel with China's world champion Qin Haiyang in the 100m breaststroke.
World record-holder Peaty is trying to match swimming legend Michael Phelps and win a third straight gold medal in the same event in a clash with Qin that is laced with intrigue.
Qin, the 200m world record-holder, was reportedly among the 23 Chinese swimmers who tested positive for a banned drug in late 2020 to early 2021.
He and Chinese swimming chiefs have denied wrongdoing, saying they tested positive after inadvertently consuming tainted food during domestic competition.
A victory for Qin on Sunday will almost certainly reignite the doping controversy that has loomed over swimming in the build-up to the Olympics.
Peaty's tussle with Qin is one of three swimming golds to be decided on Sunday.
France's great swimming hope Leon Marchand will chase glory in the men's 400m individual medley, while the women's 100m butterfly title will also be on offer.
Biles makes Olympic return
Elsewhere Sunday, American gymnastics queen Biles returns to the Olympic stage for the opening qualifying rounds.
Biles, who won four golds at the 2016 Rio Olympics, withdrew from multiple events at the Tokyo Games as she battled the disorientating condition that gymnasts call "twisties".
She still went home with a silver and bronze and won plaudits by talking openly about mental health struggles.
After taking two years out, Biles made a triumphant comeback at the US Classics last year. That was followed up by four world titles to take her tally to an astonishing 23.
Biles has been carefully shielded from the media spotlight since arriving in Paris in an attempt to ease the pressure on the 27-year-old's shoulders, and is unlikely to speak until after she has finished competing.
In other action on Sunday, the United States' star-studded basketball squad spearheaded by LeBron James and Stephen Curry will launch their quest for a fifth straight gold medal against Serbia, who are led by three-time NBA MVP Nikola Jokic.
Nadal tennis doubt
In tennis, meanwhile, there are serious questions over Rafael Nadal's participation in the singles at Roland Garros after he teamed up with Carlos Alcaraz to win their men's doubles opener.
Nadal is still listed to face Hungary's Marton Fucsovics on Sunday, with Novak Djokovic lying in wait, but the 14-time French Open champion has a thigh injury and said on Saturday he was uncertain if he would play or not.
After the rain-sodden start to the games on Saturday, Paris awoke on Sunday to blue skies and sunshine, with a heatwave forecast early next week.
However the improved weather failed to prevent the first triathlon training session in the River Seine from being cancelled on Sunday.
Following a meeting "on the water quality" and tests, "a joint decision was taken to cancel the swimming part of the triathlon orientation," a Paris 2024 and World Triathlon statement said.
Organisers blamed rain in recent days and said they were "confident" the water quality would improve enough before the triathlon competition is due to start on July 30.
Meanwhile, beach volleyball, being staged in the shadow of the Eiffel Tower, will come under the spotlight when convicted rapist Steven van de Velde plays for the Netherlands.
He was convicted in 2016 of raping an underage girl and sentenced to four years in prison.
The Netherlands' decision to pick the 29-year-old sparked outrage in the lead-up to the Games and he is not staying at the athletes' village.
