RIO DE JANEIRO — The Olympic gymnasts were back at it Sunday afternoon after a two-day break, and tiny Simone Biles — the seemingly unflappable 4-8 dynamo who already clinched all-around and team gold medals — proved her superiority once again.

Biles, competing in the vault-apparatus final, collected her third gold, soaring off the vault horse and landing in the history book with a score of 15.066, which was .700 better than silver medalist Maria Paseka of Russia — a staggering gap by gymnastics standards. Giulia Steingruber of Switzerland took bronze.

Biles became the first U.S. woman to win an Olympic gold medal in the vault. She is also the first American gymnast to win three golds in a single Olympics.

The vault was considered Biles’ weakest event, as she had never won a world title in the event. But she upgraded one of her two vaults — the Cheng — to make it more competitive with the top vaulters. The strategy paid off. She recorded the highest score of the event (16.033) on that move, which consists of jumping onto the springboard and doing a half twist before launching off the vault to a flip with 1{ twists.

“There’s a lot of satisfaction winning gold on vault, finally,” Biles said. “I’m just super excited because I was able to upgrade my second vault, and it’s exactly what I needed to do. I think it’s an amazing accomplishment (to make history).”

Her medal was one of three won by American gymnasts Sunday. Madison Kocian of Dallas won the silver medal in the uneven bars, behind Aliya Mustafina of Russia, and Alex Naddour of Queen Creek, Arizona, got the bronze on pommel horse. Naddour’s medal was the first for the U.S. men’s team at these Games and ended a 32-year U.S. drought in the event.

Biles will have a chance to win two more individual medals — in the balance beam Monday and the floor exercise Tuesday.

Asked if she can tell her three gold medals apart, she flashed the megawatt smile that has graced magazine covers and newspaper front pages and said: “You can tell which is which because on the bottom they are engraved. This one says women’s vault. The other one says women’s all-around and then women’s team.”

Biles, 19, would not reveal where she is storing her medals, although she did say she allowed her family members to pose with them around their necks.

A gymnast who did not win a medal got one of the loudest cheers of the day. The crowd gave a huge ovation to 41-year-old Oksana Chusovitina of Uzbekistan, competing in her seventh Olympics. She is the oldest female Olympic gymnast in history. Her first Olympics was Barcelona in 1992, five years before Biles was born.

Chusovitina, who has a 16-year-old son, was sandwiched between two 16-year-old gymnasts in the vault completion. Despite her age, she was one of just two competitors who attempted the dangerous Produnova vault, which carries a 7.0 level of difficulty and is nicknamed “vault of death.”

Dipa Karmakar of India was the other gymnast who did the Produnova, and she finished fourth.

Chusovitina botched her landing and wound up in seventh place. Nevertheless, she was showered with love as a tribute video of her career played on the jumbo screen. She stepped out to the middle of the arena, waved at the audience and made heart with her hands.

Asked about Chusovitina’s longevity, Biles’ coach Aimee Boorman said: “It’s ridiculous. It’s just amazing. I’m so glad she jumped up on podium afterward and waved to everybody. I’m sure she could feel the love from the arena for all she’s brought to the sport. You don’t have to be 16 years old and retire by 18. You can keep going as long as you take care of your body.”

Meanwhile, American Gabby Douglas, the all-around champion of the 2012 London Olympics, finished seventh in the uneven bars and did not qualify for any other finals. She conceded afterward that she was “a little bit upset that it really didn’t go like it normally goes” but said she would still “rejoice” in making a second Olympics.

When reporters asked if her Olympic experience was ruined by critics who called her out for not putting her hand on her heart during the national anthem — following the criticism of her hair at the 2012 Games — Douglas’ eyes teared up. Somebody dubbed her “Crabby Gabby” on social media this week, and she was clearly hurt.