Tragic news in the boxing world … undefeated fighter Musa Yamak died during a match on Saturday — after he suffered a heart attack in the ring and collapsed to the mat.

The awful scene went down in Germany … when Yamak was in the middle of his fight with Hamza Wandera.

Yamak had reportedly taken at least one big blow from Wandera in the second round … and as he was coming out of his corner for the third round of the scrap — he stumbled, and eventually crumpled to the ground.

Trainers and other medical personnel on the scene rushed to his aid — but, sadly, Yamak later passed away.

He was just 38 years old.

Turkish official Hasan Turan mourned the death in a social media post hours after the tragedy … saying, "I wish God’s mercy on the deceased … my condolences to his sad family and fans."

Yamak — who turned pro in 2017 — had built an impressive resume in his career, starting 8-0. In 2021, he gained notoriety after winning the WBFed International title.

RIP.