Patrick Day has died aged 27 after spending the last four days in a coma following his fight against Charles Conwell.
The American boxer was knocked out in the 10th round of the bout and was carried away from the ring on a stretcher.
He failed to respond to treatment after undergoing brain surgery.
A statement from his team reads:
"Patrick Day passed away today, October 16, 2019, succumbing to the traumatic brain injury he suffered in his fight this past Saturday, October 12, at the Wintrust Arena in Chicago, IL.
"He was surrounded by his family, close friends and members of his boxing team, including his mentor, friend and trainer Joe Higgins.
"On behalf of Patrick's family, team, and those closest to him, we are grateful for the prayers, expressions of support and outpouring of love for Pat that have been so obvious since his injury.
"Patrick Day didn't need to box. He came from a good family, he was smart, educated, had good values and had other avenues available to him to earn a living.
"He chose to box, knowing the inherent risks that every fighter faces when he or she walks into a boxing ring.
"Boxing is what Pat loved to do. It's how he inspired people and it was something that made him feel alive."
Promoter Eddie Hearn also tweeted his condolences on Wednesday evening.
"Devastated to hear the news of the passing of Patrick Day," he tweeted.
"I met him for the first time last Thursday, what a charming young man with a dream and a smile that lit up the room.
"Our deepest prayers are with his family, his trainer Joe Higgins, Charles Conwell and promoter Lou DiBella."
Rest in peace, Patrick.News Now - Sport News