Incoming Blues boss Antonio Conte is determined to strengthen his defence this summer and he has earmarked a number of targets.
Juventus star Leonardo Bonucci is high on Conte’s shortlist, as is Everton centre-back John Stones.
However, according to Gazzetta dello Sport, Chelsea are prepared to shell out £24m to land Koulibaly.
The 24-year-old was linked with the likes of Southampton and Norwich last summer but after a brilliant season in Italy his stock has risen.
Now Arsenal, Chelsea and Manchester United are all after the Senegal international and he is expected to leave Naples for a hefty transfer fee.