UFC Fighter Allan Nascimento Dead At 34

UFC fighter Allan Nascimento, who just fought in June, is dead ... the promotion announced Monday afternoon, shocking fans.

He was only 34 years old.

The UFC says Nascimento was located after suffering a medical emergency overnight ... and despite the best efforts of first responders, Allan couldn't be saved.

"This morning, Monday, August 3rd, our beloved flyweight fighter, Allan Nascimento, was found unresponsive after suffering an apparent heart attack in his sleep," the official statement reads.

"Despite the efforts of the responding medical team, he was pronounced deceased at the scene."

Nascimento -- known as Puro Osso" -- was a grappler from Brazil ... who'd been with the world's most popular MMA promotion since 2021.

Allan trained at Chute Boxe in São Paulo, alongside the likes of Charles Oliveira. He was a black belt in Brazilian Jiu Jitsu and was known for his slick submissions.

Nascimento was 22-7 as a pro fighter, and 4-2 inside the Octagon. He most recently fought on a Fight Night card in Las Vegas on June 20.

The MMA world, just now learning of the tragic loss, is reacting with pure shock ... with everyone from Dustin Poirier to Henry Cejudo and Mackenzie Dern sending condolences over the loss.