Thursday's theme in Rio was the head-to-head competition among some of America's biggest stars in marquee events.
In the gymnastics arena, Simone Biles topped teammate Aly Raisman to claim the sport's most prestigious title, the individual all-around, giving her a second gold following the U.S. team victory on Tuesday night.
She wasn't the only American named Simone to take gold. Simone Manuel became the first African-American woman to win an individual gold when she tied Canada's Penny Oleksiak for first in the 100-meter freestyle. The two women set an Olympic record of 52.70 and shared the top of the medal podium.
Also in the pool, Michael Phelps left the entire field far behind, including his green-haired teammate Ryan Lochte, in the 200-meter individual medley, an event the pair have dominated for more than a decade.
And American Kayla Harrison won gold in women's 78 kg judo, defending her title from London four years ago.
Here are Thursday's highlights:
Biles, Raisman go 1-2 in the all-around
Biles has been the best female gymnast in the world since 2013, but Thursday's all-around competition was the moment when she could stake her claim on the sport's biggest stage.
She led after the first event, the vault. But on the uneven bars, her least favorite event, she fell a fraction of a point behind Russia's Aliya Mustafina.
Biles had a strong 15.433 score on the balance beam, moving past Mustafina, who scored a more than a point and half lower.
In the final event, the floor exercise, Biles pulled away with another big score of 15.933, while Raisman also produced an excellent performance with a 15.433, pushing her past Mustafina.
While the spotlight was on Biles, it was also a sweet comeback for Raisman, the oldest member of the five-woman U.S. team at 22. She tied for third with Mustafina in the all-around at London four years ago. But under the tiebreaker system, Mustafina got the bronze and Raisman lost out.
The team gold for the American women on Tuesday, combined with Thursday's performance, was powerful proof of U.S. dominance in the sport.
This marked the fourth straight time an American woman has won the individual all-around, with Biles following Gabby Douglas in 2012, Nastia Liukin in 2008 and Carly Patterson in 2004.
Before Thursday, the only time American women had taken both gold and silver in the all-around was in 2008, when Liukin won and Shawn Johnson took second.
Phelps wins fourth gold in Rio
There was huge anticipation in advance of the men's 200-meter individual medley, where Phelps, 31, and Lochte, 32, have been dueling it out at the Olympics and world championships since 2003.
But Phelps left the everyone in his wake, winning by a huge margin in 1:54:66, almost two seconds ahead of silver medalist Kosuke Hagino of Japan. Phelps became the first swimmer ever to win the same Olympic event four times. The victory also gave him his fourth gold in Rio, with more opportunities to come.
Lochte, whose dyed blond hair has turned green in the pool, was just a tick behind Phelps in the semifinals. But he faded to fifth in the finals.
Phelps, meanwhile, now has 22 golds and 26 medals overall in five Olympics.
As Phelps and Lochte wind down their Olympic careers, two young Americans, Manuel, 20, and Ryan Murphy, 21, have made big splashes in their first Olympics.
Manuel used a late push to take the 100-meter freestyle, an exceptionally close race where all eight finishers were separated by less than seven-tenths of a second. As she turned around to look at the scoreboard, she gasped when she learned she had tied for first.
Murphy won gold in the 200-meter backstroke Thursday night to go with his gold in the 100-meter backstroke on Monday.
Kayla Harrison gives the U.S. a rare gold in judo
Kayla Harrison became the first American, male or female, to win Olympic gold in judo four years ago. On Thursday, she became the second American to win gold, successfully defending her title in the 78 kg weight class at Rio's Olympic Park.
The effervescent Harrison faced France's Audrey Tcheumeo in the final, which was close until Harrison took Tcheumeo down with an ippon that ended the match in the final minute.
Harrison, 26, is expected to retire from judo and has said she's contemplating joining the Ultimate Fighting Championship.
Harrison has spoken out about sexual abuse she suffered at the hands of a former coach, which began when she was 13 and lasted for three years, taking place at times when they traveled to judo competitions. She later testified against the coach, who was sentenced to 10 years in prison.
She credits her current coach, Jimmy Pedro, with helping her emotionally and as a judoka. Pedro won two bronze medals at the Olympics, and until Thursday, was the only American with more than one Olympic medal in the sport.
Now he has company.
Fiji wins its first gold
Tiny Fiji has been going to the Olympics since 1956, yet no athlete from the South Pacific nation had ever made it to the medal stand.
However, Fiji's national sport, rugby, returned to the games this year after a 92-year absence, and the island nation made the most of it.
Fiji thumped Great Britain, its former colonial ruler, 43-7, to take the gold medal in seven-on-seven rugby Thursday. The game was all but over by halftime as Fiji raced to a 29-0 lead in this fast-paced, high-scoring version of the game.
Fiji, which has a population of just 900,000, regularly holds its own against much larger countries in international rugby.
Golf returns to the Olympics after 112 years
Australia's Marcus Fraser fired an eight-under-par 63 and Great Britain's Justin Rose hit a hole-in-one on the 4th hole as golf returned to the Olympic Games on Thursday for the first time since the 1904 Games in St. Louis.
With many of the top names in golf opting out of Rio, citing Zika and security concerns, the field has been left wide open for lesser-known players like Fraser, who took a three-stroke lead at the end of the opening round.
"I think this is probably one of the best rounds of golf I've ever played," Fraser told the Golf Channel. "I was quite edgy and a bit jumpy on the first tee because it's such a big occasion to be here at the Olympics. To manage that and go on to play the way I did is really pleasing and a big confidence boost."
The top performer on the four-man American team was Matt Kuchar, who shot a two-under 69 and is tied for 11th place. The three other Americans in Rio, Patrick Reed (+1), Bubba Watson (+2) and Rickie Fowler (+5), were all over par.