The defender has been one of Napoli's star performers over the past 18 months and he has been watched by several clubs.
Chelsea reportedly failed with a huge bid of close to £50m in the summer of 2016, while Everton have also been tracking him.
But now, according to Mundo Deportivo, Barcelona are considering a January swoop for Koulibaly.
The Spanish giants are said to be looking for a new centre-back and they have earmarked the 26-year-old as a top target.
However, Koulibaly is unlikely to come cheap and Napoli could ask for close to £60m for his signature.