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.
Already considered the greatest gymnast of all time, the American Biles made another piece of history as the first woman to regain the Olympic all-around title, having won it in 2016.
After winning Commonwealth gold in 2022, Montag said: "Towards the end of the Holocaust (in mid-January 1945) they marched through snow and cold for days on end in little sandals and hardly any clothing.
World number seven Zheng triumphed 6-2, 7-5 and will face either Croatia's Donna Vekic or Anna Karolina Schmiedlova of Slovakia in the gold medal match.
Pan smashed his own record with a time of 46.40 seconds in the last race of the night at the La Defense Arena on Wednesday. Australian silver medallist Kyle Chalmers was a massive 1.08 seconds behind.
With her victory, Yang added "Olympic champion" to a resume that already included world record-holder and 2017 world champion.
There will be 18 gold medals up for grabs in France, including four each in rowing and swimming, plus two each in judo, sailing and athletics, while Olympic champions will also be crowned in shooting, artistic gymnastics, and fencing.
Pan powered to the finish in 46.40sec, beating the world record time of 46.80 he had set in February in Doha. It was China's first swimming gold of the Paris Games.
American great Ledecky again set new standards, cementing her reputation as the greatest distance swimmer the sport has known.
When doctors x-rayed his spine after the crash in 2021, "they said maybe I'll never walk normally again," an emotional Lind told AFP after his win on Wednesday.
For Ni, a former world champion with China who now represents Luxembourg, her stint in Paris was a dream come true.