U.S. gymnastics star Simone Biles won her fifth gold medal in the women's floor final Sunday to conclude her "best ever" world championships and take her career record to 25 medals.

Biles, who won the beam title earlier in the day, also claimed an unrivaled 19th world gold following her previous successes in the team, all-around and vault events in Stuttgart.

"This is really the best worlds performance I have ever put out," she said after finishing her fifth world championships with five titles in six events.

The 22-year-old plans to celebrate when she gets back home to Texas, where "my mom usually likes to throw a worlds party – whether I want one or not," she joked.

Biles was crowned world floor champion for the fifth time after winning by a full point from team-mate Sunisa Lee, who earned silver with Russia's Angelina Melnikova taking bronze.

"I just couldn't move at the end, I was so tired," Biles confessed after her sixth and final event in Stuttgart.

Her double gold success Sunday came within a two-hour spell after earlier winning the beam final with Liu Tingting, 19, taking silver and 16-year-old Li Shijia claiming bronze.

"It meant a lot," said Biles of her gold on the beam. She had to settle for bronze in the event at the 2016 Olympics and last year's world championships in Doha.

"I'm thrilled with that performance, it was probably the highlight" of the week.

Biles worked hard on the beam to rebuild her confidence in the discipline, so "to go out there and nail the routine felt really good."

Sunday's golds made Biles the most decorated gymnast in world championship history, surpassing the previous all-time record of 23 world medals won by men's star Vitaly Scherbo of Belarus in the 1990s.

This is the first time she has finished a world championships with five golds, but she has said she is "99 percent" sure Stuttgart will be her last.

The only blot on her near-perfect record in southwest Germany came in Saturday's uneven bars final when she finished fifth, but both Biles and her coach Laurent Landi were delighted with her week.

Less than 10 months before the Tokyo Games, Biles is on course to retain the Olympic team, floor, vault and all-around titles she won in Rio.

"She's incredible, she was here to do a job and she did exactly what she trained for," said Frenchman Landi.

"She has shown to herself and everybody else that she is consistent, not only in training, but when it counts.

"If she does this for 12 more months, she will be very, very successful."

Landi said the hard work Biles has also put into her mental preparation paid off as she patiently waited despite a lengthy delay before her floor routine while judges reviewed a rival's performance.