In short:

Italy's Sara Curtis, 19, has broken the women's 50m backstroke world record, previously held by Australian Kaylee McKeown.

Curtis set the new mark at 26.63 seconds ‌in the semifinals of the European championships.

McKeown, a five-time Olympic champion, is recovering from glandular fever that forced her out of the Commonwealth Games and this week's Pan Pacific Championships.

Italian teenager Sara Curtis has set a new world record in the women's 50m backstroke, beating the mark previously held by Australian great Kaylee McKeown.

Curtis smashed the Queenslander's 50m global mark in 26.63 seconds ‌during the semifinals of the European championships in the ‌Paris Olympic pool on Wednesday, local time.

That slashed nearly a whopping quarter-of-a-second off McKeown's mark of 26.86 set at a World Cup meet in Budapest, Hungary, in October 2023.

Curtis, born in Savigliano to an Italian father and a Nigerian mother, has been making dramatic strides since attending the swimming powerhouse University of Virginia.

She had signalled her form by winning bronze in Tuesday's 100m freestyle at the Europeans, but she was stunned by her record-breaking swim.

"I knew I was capable of doing it, but I didn't expect it here, in this race, in this moment," the youngster beamed.

"It's just so awesome, and I'm so happy! I can tell that I am superwoman right now, it's unbelievable, and I don't think I'm going to be able to sleep tonight."

There were other warning signs for 25-year-old Queenslander McKeown, with Russian Alina Gaifutdinova coming home ‌second-fastest in the semifinals in 26.91, the third-fastest time in history.

When McKeown recorded her 50m time in 2023, she was the first swimmer to hold the 50, 100 and ‌200m backstroke world records simultaneously.

Now, though, McKeown only holds the 200m mark after losing the 100m record to US rival Regan Smith in June ⁠2024.

McKeown, a five-time Olympic champion, is recovering from glandular fever that forced her out of the Commonwealth Games and this week's Pan Pacific Championships.

AAP/ABC