The 25-year-old was heavily linked with a move to Chelsea ahead of the 2016-17 campaign, with Napoli president Aurelio De Laurentiis claiming the Premier League leaders were ready to pay close to €60million for the centre-back.
Napoli refused to sell Koulibaly, though, tying him to a new deal in September and he has been a key figure at the San Paolo again this season as they chase Champions League qualification, with the Serie A club able to call the shots on any offers that are forthcoming.
"We renewed with Napoli until 2021, so Kalidou will stay at Napoli," his agent Bruno Satin told Radio Crc.
"He will not move from Napoli, everything is in order with the club.
"A release clause? There is no clause. These are private and confidential matters between the club and the player."