Great Britain's Keely Hodgkinson made a winning start to her Olympic 800m title bid as Joshua Cheptegei claimed the first track gold at Paris 2024 in the 10,000m.
Hodgkinson, 22, is targeting a first global crown after finishing second at successive World Championships since she clinched a stunning silver on her Olympic debut as a teenager in Tokyo.
She controlled her heat from the front in one minute 59.31 seconds to qualify for Sunday's semi-finals, where she will be joined by team-mates Jemma Reekie and 17-year-old Phoebe Gill.
World record holder Cheptegei, of Uganda, sprinted clear on the final lap to set an Olympic record of 26:43.14 and clinch the first gold on the eye-catching purple track inside the Stade de France.
The 27-year-old, a three-time world champion over 10,000m, finished ahead of Ethiopia's Berihu Aregawi and bronze medallist Grant Fisher, of the United States.
Elsewhere, Great Britain will compete for a mixed 4x400m relay medal on Saturday after the quartet of Samuel Reardon, Laviai Nielsen, Alex Haydock-Wilson and Nicole Yeargin set a national record to win their heat in 3:10.61.
The United States qualified fastest for that final in a new world record of 3:07.41.
However, Team GB's Scott Lincoln was unable to qualify for the shot put final with a best throw of 19.69m.
The French athletes were backed passionately throughout the evening and, in a remarkable moment, the men's decathlon 400m was delayed by loud chants of 'Allez les Bleus' when swimming superstar Leon Marchand won his fourth gold of the Games.
Josh Kerr and rival Jakob Ingebrigtsen remain on course for their anticipated Olympic gold-medal showdown after both qualified from their men's 1500m heats in Friday's morning session.
Hodgkinson's confident start as all three Brits progress
By a combination of her own sustained development and determination, and the misfortune suffered by one of her biggest rivals, Paris represents Hodgkinson's best chance yet of landing global gold after a series of near-misses.
The Briton has run one second quicker than any other woman this year after smashing her own national record in 1:54.61 at the London Diamond League a fortnight ago, having defended her European title in June despite battling illness.
With Athing Mu unable to defend her Olympic title after falling at the US trials, one of the 'big three' of women's 800m running has been removed from the equation, leaving Kenya's reigning world champion Mary Moraa as Hodgkinson's greatest threat to reaching her goal.
Moraa qualified second in her heat, with her time of 1:57.95 the second-fastest overall behind Tsige Duguma of Ethiopia (1:57.90).
"[The heats are] worse than the final. In the final you know you're just giving it everything," Hodgkinson said.
"You've got to contend with people giving it their absolute all. You want to conserve energy but at the same time you don't want to make any mistakes. Definitely glad that's done, the semi-finals will be more fun."
Mu's absence has also opened the door for the other two Britons, with Reekie, 26, hoping to go one better than her agonising fourth in Tokyo and Gill looking to ride the wave of a sensational breakout season.
Reekie won the opening heat in 2:00.00, while Gill - Britain's youngest Olympic track athlete in 40 years - finished third in her race in 1:58.83.
Gill said: "It's the Olympics, it's the best competition in athletics, and seeing my face on the screen I was trying my best not to cry."
What is happening in the athletics on Saturday?
British sprinters Dina Asher-Smith, Daryll Neita and Imani-Lara Lansiquot will aim to reach the women's 100m final at 18:50 BST.
American world champion Sha'Carri Richardson and Jamaica's two-time Olympic 100m gold medallist Shelly-Ann Fraser-Pryce will also be in semi-final action, with the final taking place at 20:20.
Before then, Great Britain will contest the mixed 4x400m relay final at 19:55.
The men's 100m competition gets under way during Saturday's morning session, with Team GB's world bronze medallist Zharnel Hughes, rising star Louie Hinchliffe and Jeremiah Azu contesting round one from 10:55.
That will also see the start of American Noah Lyles' bid for a potential four golds in Paris.
Sweden's Armand Duplantis will begin his pursuit of a fourth successive global gold when the men's pole vault qualification takes place from 09:10.
