The Senegal international measures in at a whopping 6 foot 5 and was in fantastic form last season, averaging 2.5 tackles, interceptions and successful aerial duels per match as Napoli claimed a runner-up finish in Serie A.
According to Gazzetta dello Sport, the Toffees have identified the 25-year-old centre-back as the ideal replacement for John Stones, who is reportedly on the verge of a £53million move to Manchester City.
Everton are even prepared to shell out a club-record £42million transfer fee to convince Napoli to sell Koulibaly, who is currently amid a contract dispute at Stadio Sao Paolo.
But the Italian website warn that the Goodison outfit will have to fend off interest from Premier League rivals Chelsea, who are also keen on the dominant centre-back. London Evening Standard also reported on the Blues’ interest earlier this week.