Hulk Hogan just appeared on the Howard Stern show ... and admitted the woman in his sex tape is the estranged wife of his best friend, Bubba the Love Sponge ... who gave Hulk his blessing to nail her.
Hulk spilled his guts to Stern ... saying Bubba -- a nationally syndicated radio DJ -- allowed Hogan to have sex with Heather Clem six years ago.
During the interview, Hogan says he was still married to Linda at the time of the sex tape ... but says she drove him to have sex outside the marriage because she was so verbally and emotionally abusive to him.
Hulk also admitted his performance wasn't exactly tip top.
Hogan says he's working with officials to find out who released the tape ... because he swears he didn't know he was being recorded ... and vows to press charges against the perpetrator.