Gary Michael Hilton is one of the oldest living serial killers in the country … and now he’s confessing for the first time to the murder that landed him on Death Row in Florida.

The 78-year-old Hilton — AKA The National Forest Serial Killer — sat down with Court TV’s investigative reporter David Scott — and TMZ has obtained an exclusive clip of their recent face-to-face interview … and it’s pretty damn wild!

But first, just to recap … Hilton was convicted of killing four people during his monstrous 2007-2008 spree in three states: Florida, North Carolina and Georgia. He committed the murders in national parks and confessed to three of them, but he never copped to the fourth — a nurse named Cheryl Dunlap, who was killed in 2007 in Leon County, Florida. That is, until now.

Check out the video … it begins with Scott talking about how Hilton is a total nightmare to all women — and Hilton relishes in the moment, clearly loving the media attention. Scott then segues to the kidnapping and dismembering of Dunlap — a devout Christian.

Hilton is more than happy to discuss the Dunlap case — which he says is currently under appeal — but it doesn’t matter … Hilton tells Scott he’s gonna give the reporter a big scoop and confess to her brutal slaying.

In another interview clip, Hilton claims he’s in poor health, suffering from congestive heart failure and says he doesn’t have much time left to live. That’s why he’s decided to give Scott the interview, vowing to answer any question the journalist throws his way.

After 17 years of keeping his dark secrets locked away with him on Florida’s Death Row, Hilton promises to give Scott a “Lollapalooza” interview that will “knock your socks off.” He describes himself as a “different breed” of serial killer who is partly a sociopath.