Rocco B. Commisso, the billionaire chairman of the cable provider Mediacom, is the new owner of the Italian soccer club A.C.F. Fiorentina in a deal he described as the “quickest closing in soccer history.”

Commisso, who was born in southern Italy but moved to the United States when he was 12, said in an interview on Thursday that the deal was completed within three weeks of his signing a letter of intent to acquire the Florence-based team, which only avoided relegation to the second division on the final day of the Serie A season.