Millwall's owner and chairman John Berylson has died at the age of 70 following a "tragic accident" on Tuesday, the club have said.
The American businessman first became involved with the Championship club in 2006.
"He was a truly great man, incredibly devoted to his family," Millwall said in a statement.
Berylson is survived by wife Amy and his three children Jennifer, James, and Elizabeth.
The club added: "He was a person of such remarkable generosity, warmth, and kindness.
"He lived a storied life, one full of colour and joy, and was infinitely thoughtful of others with an endless desire to share his immense knowledge and experiences to help people."
Millwall have not released any further details around Berylson's death.
The club have said fans can pay their respects in a book of condolence which will be shared with his family.
Supporters can write in the book at the club's The Den stadium on Wednesday from 11:00 BST, or online.
