Peyton Manning Sexual Assault Deposition Video Surfaces

For the first time, video of Peyton Manning's deposition -- in which he denies sexually assaulting a former University of Tennessee trainer -- has gone public.

Peyton sat for the deposition back in 2003 ... after Dr. Jamie Naughright sued him for defamation over a chapter in his autobiography about the 1996 incident.

Naughright had accused Manning of shoving his testicles and anus into her face while she was examining him on a training table at UT.

Manning claims he was simply trying to "moon" a friend -- and in the deposition video, obtained by "Inside Edition," he explains:

"I briefly pulled down my pants to so-called 'moon' him. One second, one and a half seconds. Pulled my pants back up and continued with Jamie's examination of the bottom of my foot."

Naughright says Manning is lying and refused to back down during an interview with "Inside Edition."

Manning's attorney is adamant the NFL legend did nothing wrong.