It was the sixth time McLaughlin-Levrone had broken the world record, lowering her previous mark of 50.65 set at the U.S. trials in June.
Lyles, who had been bidding to complete a 100m-200m double in Paris, was taken off the track in a wheelchair following the race, won by Botswana's Letsile Tebogo.
The 26-year-old, who had claimed virtually every other title in an utterly dominant half decade including three world championship gold medals, clocked 12.99 seconds.
A tense game ended all square at 1-1, with fourth-quarter goals in quick succession from Dutch captain Thierry Brinkman and Germany's Thies Prinz.
Nadeem threw an Olympic record of 92.97 metres for victory, India's defending champion Neeraj Chopra taking silver with 89.45. Grenada's Anderson Peters claimed bronze with 88.54m.
Marathon swimming is set to get underway amid concerns over water pollution in the river Seine.
There will be 21 medals up for grabs with the bulk of them being given out in athletics.
"The last hurrah, I'm done. I've always said I want to retire a champion, that's it," Harrington told Irish national broadcaster RTE.
Alfred is seeking to emulate Jamaica's Elaine Thompson-Herah, who did the 100m-200m double at the Rio 2016 Games and at the Covid-delayed Tokyo Olympics.
The 22-year-old was greeted with a massive roar when he entered the arena and the noise did not let up until long after he had touched the wall in an Olympic record time.
The hottest ticket in town will be at Roland Garros, where Novak Djokovic and Rafael Nadal will clash for a 60th time, with the Serb up in their rivalry 30-29.
The 17-year-old French-born athlete earned an impressive 15.600 points for her bars routine -- an acrobatic, gravity-defying performance full of technical skill and difficulty at Bercy Arena.
A galaxy of A-listers, from Hollywood star Tom Cruise to Vogue editor-in-chief Anna Wintour, crowded into a packed Bercy Arena to watch as Biles began her quest for Olympic redemption.
The down-to-earth 23-year-old held off Canadian teenager Summer McIntosh and American great Ledecky to join Dawn Fraser as the only Australian female swimmer to retain an Olympic crown.
Simone Biles will make her eagerly anticipated first appearance at the Paris Olympics on Sunday while British breaststroke king Adam Peaty aims to emulate Michael Phelps in the swimming pool.
McKeon, who was the star act in Tokyo and is at her last Olympics, won her sixth gold and 12th medal overall.
The 38-year-old effectively ruled himself out of the singles tournament as he battles a thigh injury picked up in training at Roland Garros, the scene of 14 of his 22 Grand Slam triumphs.
French heavy metal band Gojira set the bar high during they 2024 Paris Olympics Opening Ceremony performance, which included a headless Marie Antoinette.
Thousands of Olympic competitors cruised down the River Seine in a spectacular opening ceremony for the Paris Games on Friday that celebrated French history and culture to the delight of a crowd undeterred by persistent rain.