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.
"It's gorgeous, everybody is calling it the Barbie Dreamhouse," U.S.-born gymnast Luisa Blanco, who is representing Colombia, told Reuters.
It was a shattering blow for the 22-year-old, who finished third at the 2022 world championships and was primed for a strong showing in Paris.
Strong thunderstorms, heavy rain, hail and lightning were likely from 6:00 pm (1600 GMT) over the French capital, the weather service announced in a bulletin.
The 33-year-old produced a remarkable comeback from 11-5 down to wrest the bronze from South Korea's Choi Se-bin in front of a crowd containing her mother, sister and nephew -- her father is not able to leave Ukraine.
Organisers previously said they were confident water quality would improve in time for the race after heavy rains last Friday and Saturday dirtied the river.
Through the difficult moments, it was his teammates' unwavering determination and constant encouragement that carried him through, Hashimoto said.
"What appears to you as two players on the podium, they were actually three! It was me, my competitor, & my yet-to-come to our world, little baby!" Hafez wrote on Instagram.
Murphy, a seven-times Olympic medallist, married Bridget Konttinen last year and the 29-year-old swimmer said they will be welcoming a child in January.
Biles makes her second appearance at the Paris Games in the women's team final, where she hopes to win a fifth Olympic gold medal for the United States.
The Italian, who was fourth in Tokyo, delivered Italy more joy following Nicolo Martinenghi's triumph in the 100m breaststroke on Sunday.