Antonio Conte has quit as coach of Juventus just a day after the squad reconvened for pre-season training.
Conte, who had a year remaining on his contract, led the Turin club to the Serie A title in each of the past three years.
But the 44-year-old said he felt it "may be more difficult to keep winning with Juventus" in the future.
"I have matured with time and my feelings led me to make this choice," he added.
Juventus chairman Andrea Agnelli said the news of Conte's departure, which was announced on the club's website, "saddens me greatly".
Conte is a former Italy international who made over 500 appearances for Juventus in his playing days, winning five league titles.
He returned to Juve as coach in 2011 and went on to preside over one of the most successful periods in the club's history.
He won Serie A at the first attempt with his side going unbeaten throughout the season. A second title followed but the summer of 2012 saw him embroiled in a corruption row after he was charged with failing to report attempted match-fixing during his time as coach of Siena.
Conte pleaded his innocence but was banned for 10 months - a sentence reduced to a four-month touchline suspension last August.
He returned to the dugout midway through last season to lead Juve to another title.