Almaz Ayana of Ethiopia set a world record in the 10,000 meters with a stunning solo run to win the first gold medal of the athletics program. Vivian Cheruiyot of Kenya took silver.
Ayana finished in 29 minutes, 17.45 seconds. The old record of 29: 31.78 of China's Wang Junxia stood since 1993.
At 24, Ayana is now poised to become the next dominating long-distance runner and is also going for gold in the 5,000 meters next Friday. She is unbeaten this season.
Tirunesh Dibaba took bronze, missing out on the chance to become the first woman to win three individual gold medals in a row.
Britain's rowing team has clinched a second consecutive gold in Rio by winning the men's four ahead of Australia.
It was the country's fifth consecutive Olympic title in an event that's become as British as afternoon tea.
Alex Gregory, Mohamed Sbihi, George Nash and Constantine Louloudis were in a tight race with Australia's four with only two-tenths of a second separating the crews at the half-way mark.
But the Australians fell back in the latter half of the race as the Brits won by nearly two seconds. Italy got the bronze.
Britain has won a total of nine gold medals in the men's four. The only country that has more Olympic titles in a rowing event is the United States, which has 12 in the men's eight.
Germany's Henri Junghaenel has captured gold in men's 50-meter prone rifle after an impressive shooting display.
Junghaenel, a four-time All-American at the University of Kentucky, hit a near-perfect 10.8 four times in his first Olympics to outlast South Korea's Jonghyun Kim. Junghaenel briefly lost the lead to Kim late in the finals, but closed out gold with a 10.7 and 10.4 on his final two shots to finish 1.3 points ahead of Kim.
Kim tied Russian's Kirill Grigoryan in the bronze medal round and hit a perfect 10.9 to win a win shoot-off to take silver.
The 24-year-old Grigoryan hit 9.7 on his final shot to earn bronze.
Usain Bolt's parents are confident he will defend his titles in both the 100 meters and 200 meters at the Rio Olympics.
Wellesley and Jennifer Bolt visited their son Thursday night in the Athletes Village and asked him if he was healthy and prepared for his final Olympics. Bolt pulled out of his national championships last month with a sore hamstring, but has insisted he's fine to compete in Brazil.
Jennifer Bolt said when she asked her son if he was ready to go Sunday, he said: "Mom, if I wasn't ready, I wouldn't be here because I'm not into the losing thing. I'm ready."
Bolt is trying to win the 100, 200 and 4x100 relay — which he has in the last two Olympics — to close his career with nine gold medals.
British rowers Helen Glover and Heather Stanning have successfully defended their Olympic gold in the women's pair.
The Brits, world champions in the event, came out of the blocks the quickest and never lost their lead on the 2-kilometer course.
New Zealand's Genevieve Behrent and Rebecca Scown were in last place after 500 meters but fought back to grab the silver ahead of Denmark's Hedvig Rasmussen and Anne Andersen.
The United States remains without rowing medals in Rio after Felice Mueller and Grace Luczak dropped to fourth place after a strong start.
Pierre Houin and Jeremie Azou won France's first rowing gold medal at the Rio Olympics, beating Ireland and Norway to the finish line in the lightweight men's double sculls.
The French world champions led the race from start to finish but the Irish and Norwegian crews came dangerously close in the final 50 meters.
Just 69 hundreds of a second separated the winners from bronze medalists Kristoffer Brun and Are Strandli of Norway.
Valerie Adams of New Zealand is on track for her third Olympic gold medal in a row, qualifying for late Friday's final of the shot put on her first attempt.
With the qualifying mark set at 18.40 meters, Adams threw 19.74 meters. German world champion Christina Schwanitz also needed one attempt only, and went through with 19.18. Michelle Carter of the United States was the only other competitor breaking the 19-meter mark with 19.01.
No woman has ever won three individual Olympics golds in a row. Before Adams' final, Tirunesh Dibaba of Ethiopia also has a shot at the feat when she starts in the 10,000 meters final later in the morning session.