According to Sky Sports, the Blues are in talks to sign the 31-year-old centre-back. The Senegalese has gained a reputation as one of the most imposing defenders in European football.
As reported by Eurosport journalist Romain Collet-Gaudin on Twitter, Koulibaly was recently quizzed about a potential transfer to Chelsea, to which he replied:
“I'll confirm that later, but it's on the right track."
Koulibaly has made over 300 appearances for Napoli following his arrival from Belgian side Genk eight years ago. He has since gone on to become captain of the Serie A giants, as well as for his country Senegal.
The defender has 62 caps for his nation and he led them to an African Cup of Nations victory earlier this year. He also helped them qualify for the Qatar World Cup, which begins in November.
Chelsea are desperate to sign top-class centre-backs this summer. Both Antonio Rudiger and Andreas Christensen left on free transfers to Real Madrid and Barcelona respectively this summer.
Chelsea chasing several top-class centre-backs during the transfer window
As referenced in the previously mentioned Sky Sports report, the Blues are weighing up their options for several central-defenders this summer. The west London club are yet to complete a signing in the current window under new owner Todd Boehly.
The report claims that the Blues are chasing Manchester City's Nathan Ake, who has found himself down the pecking order under Pep Guardiola.
The 27-year-old could be the latest player to re-sign for the Blues after he was sold to Bournemouth in 2017. They have also let go of Romelu Lukaku and Nemanja Matic in the past. However, they ended up paying big money for them again further down the line.
The Blues have long been linked with Sevilla defender Jules Kounde, who played 44 times for the La Liga side last term. The 23-year-old already has 11 French caps.
The report also names RB Leipzig's Josko Gvardiol and Paris Saint-Germain's Presnel Kimpembe as potential options for the two-time European champions.