A Barnsley supporter died while watching Wednesday night's Sky Bet Championship match against Derby at Oakwell, the club and local police have announced.
Jeffrey Wroe, 66, suffered a cardiac arrest towards the end of the game and despite being treated by the emergency services, he could not be revived.
A club statement read: "Barnsley Football Club are deeply saddened to learn of the passing of a supporter at Wednesday night's fixture against Derby County.
"Sixty-six-year-old Jeffrey Wroe was treated by emergency services at Oakwell towards the end of the match, but devastatingly, was unable to be revived.
"The club has been liaising with and will continue to support the family and friends of Mr Wroe through this exceptionally difficult time, whilst asking for their privacy to be respected."
Derby added on Twitter: "Derby County Football Club is deeply saddened to learn of this news and offers its condolences to the family and friends of Jeffrey Wroe."
South Yorkshire Police said in a statement: "Officers were alerted at 9.24pm to a man in cardiac arrest at the Barnsley vs Derby match at Oakwell.
"Despite the best efforts of the emergency services the man died."
Barnsley drew the match 2-2, and play their next match away at Preston on Saturday.