Fiorentina captain Davide Astori died of a sudden illness on Sunday morning, the Serie A club said on Twitter.
He was 31 years old.
"Fiorentina is deeply upset to have to announce that its captain Davide Astori has passed away, victim of a sudden illness," said the statement.
"Due to the terrible and delicate situation, and above all for the respect of his family, an appeal is made to everyone's sensibility."