Tennessee Highway Patrol Trooper Rex Lowery, who investigated the fatal 12:10 a.m. accident, identified the dead man as Gibson Robert Wilson, 25, of 1522 Lillian Street, Nashville.
Lowery said he understood that Wilson was a Greeneville native and apparently was visiting his home town at the time of his death. Lowery said Wilson's wife apparently was at a Greeneville motel when her husband was killed.
Greeneville police said Wilson was a one-time Greeneville High School basketball player.
Wilson was a passenger in a 1992 Cadillac driven by Barry L. Moore, 22, of Greeneville, who was seriously injured in the single-car crash, the THP said.
Moore is the brother of Dustin Moore, former Greeneville High School football star and former University of Tennessee player.
The accident took place on a straight stretch of roadway at the intersection of the Erwin Highway (Tennessee Highway 107) and the Old Jonesborough Road about two miles east of Tusculum, according to Trooper Lowery.
Lowery said Moore's Cadillac was westbound on the Erwin Highway when the driver apparently lost control. The car then veered off the right side of the roadway, went down an embankment, struck another embankment and flipped onto its left side.
During the crash, Lowery said, Wilson and Moore, who weren't wearing seat belts, were thrown from the car, with Wilson landing on Erwin Highway and Moore landing on Old Jonesborough Road.
Moore was flown by helicopter to the Johnson City Medical Center after the accident and was listed in serious condition at that hospital Sunday afternoon.
Charges against Moore are pending the outcome of the accident investigation, Lowery said.
Lowery said he was assisted at the accident scene by Greene County Sheriff's Deputies Tim Davis and Robbie Morgan and by THP Sgt. C.D. Hughes.
Also responding to the scene were units from Greene County-Greeneville Emergency Medical Services (EMS), the Tusculum Volunteer Fire Department and the Greeneville Emergency & Rescue Squad.