Playboy Mansion Deal Falls Apart ... Hef Wants His Privacy

The Playboy Mansion can still be yours, because TMZ has learned the impending sale has fallen through ... because the buyer demanded access that would disrupt Hugh Hefner's life.

The buyer was 32-year-old Daren Metropoulos, the son of a billionaire businessman, who has become a master at re-branding tired products, including Ghirardelli Chocolate and Bumble Bee tuna. We're told the purchase price was around $110 million.

The sticking point ... according to the deal, Hefner had the right to live out his life in the mansion before Metropoulos could do his thing ... restoring it and adding onto the structure. We're told Metropoulos wanted a significant amount of access during Hef's remaining years ... and Playboy felt he was being unreasonable.

The parties haggled for weeks ... sending several dozen versions of the deal back and fourth, to no avail. The deal officially fell apart Thursday night.

The Mansion is going back on the market Monday.