Mixed martial arts (MMA) fighter Allan Nascimento, who has featured in the Ultimate Fighting Championship (UFC), passed away at the age of 34 on Monday.The UFC stated that Nascimento died due to an apparent heart attack in his sleep.“Despite the efforts of the responding medical team, he was pronounced deceased at the scene,” added a UFC statement.“Our thoughts and deepest condolences are with Allan’s family, friends, teammates and loved ones during this incredibly difficult time.”This morning, Monday, August 3rd, our beloved flyweight fighter, Allan Nascimento, was found unresponsive after suffering an apparent heart attack in his sleep. Despite the efforts of the responding medical team, he was pronounced deceased at the scene.Our thoughts and deepest… pic.twitter.com/vlaBaBOyJr— UFC (@ufc) August 3, 2026Competing under the UFC banner since 2021, Nascimento last stepped into the Octagon in June, coming up just short in a split-decision loss against Mitch Raposo. That defeat brought his career record to 22-7, including a 4-2 run in the UFC.The UFC remembered the flyweight fighter from Sao Paulo as “a skilled competitor and consummate professional”.“Today I lost a brother that the fight game gave me,” legendary Brazilian MMA fighter Charles Oliveira wrote on social media.“Thank you for always being by my side, for sharing the mats and the corner. I have nothing but gratitude for having you with me – in training, in the corner, and just hanging out. I love you, man; you’re a legend.”Story continues below this adBrazilian MMA academy Chute Boxing, where Nascimento trained, also paid their tributes to “a warrior, a friend, a dedicated competitor, and an extraordinary human being”.“Allan inspired others both on and off the mats with his determination, humility, respect, and fighting spirit.“His presence will be missed beyond measure. Rest in peace, Allan; your name, your story, and your legacy will live on forever through our star,” it added.