The huge offer was swiftly turned down according to club chairman Aurelio De Laurentiis.
United have been linked with the 27-year-old for some time and former boss Jose Mourinho was a known admirer of the player who was such an important part of the Napoli team built by current Chelsea manager Maurizio Sarri. It's unlikely this will be the end of United's interest in the player but whoever comes
The 27-year-old's exploits have captured the attention of several clubs around Europe and there are likely to be more offers for the player next summer.
Talking to the media at an event held by Corriere del Mezzogiorno, De Laurentiis admitted that Mourinho made it clear he wanted the player at Old Trafford and was willing to may nearly £100million for the player.
"(Jose) Mourinho wanted him, we rejected £95 million," De Laurentiis said. "But now it's impossible that he leaves Napoli."
Mourinho was continually foiled in his bids to bring in defensive reinforcements at Old Trafford last summer. The club failed to attract all of their main targets including England and Leicester defender Harry Maguire despite being willing to pay a huge fee for the former Hull City and Sheffield United man.
United's failure to bring in players in areas where Mourinho was so desperate to strengthen was frequently cited as one of the reasons the club struggled. There had been suggestions that Ed Woodward was ready to allow Mourinho to make three new signings in January.