Chelsea were linked with a move for Koulibaly before the start of this season.
But Napoli held firm on their reluctance to sell the centre-back.
Chelsea eventually promoted Andreas Christensen to the first team as a replacement for John Terry, while Antonio Rudiger was brought in from Roma.
But Blues manager Antonio Conte has supposedly not given up hope of landing Koulibaly in the near future.
That is according to Italian outlet Calceriomercato, who claim Napoli have now named their price for the Senegal international.
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According to the report, Napoli want between £53m (€60m) and £62m (€70m) for the player.
Chelsea ended the summer with a net spend of just under £90m – the third highest outlay in the Premier League after Manchester City and Manchester United.
They will sell Diego Costa to Atletico Madrid when the transfer window opens in January, meaning they should have plenty of funds to chase Koulibaly and other targets at the end of the season.
Koulibaly has played every minute of Napoli’s Serie A campaign this season and has helped the club rise to the top of the table.
Napoli, Inter Milan and Lazio have all emerged as serious title contenders to Juventus, who languish in fourth place.
Calciomercato claim Koulibaly could be offloaded if Napoli win the league, as the club may be powerless to stop him leaving.
He is expected to play in the World Cup next summer if Senegal beat South Africa next month.