Christopher Wallace sustained gunshot wounds to his chest, shoulder, leg, forearm and scrotum on the night he was murdered in L.A. back in 1997 ... this according to the never-before-seen autopsy report, just obtained by TMZ.

The report confirms Wallace -- who was listed at 6'1", 395 lbs -- was struck a total of 4 times in a drive-by shooting on Wilshire Blvd while the 24-year-old rapper sat in the passenger seat of a Chevy Suburban.

According to the report, 3 of the shots were NOT fatal.

-- Gunshot #1 struck Wallace in the left forearm and traveled down to his wrist.

-- Gunshot #2 struck Wallace in the back, missed all vital organs, and exited through his left shoulder.

-- Gunshot #3 struck Wallace on his outer left thigh and exited through his inner left thigh.

The reports says ... after Gunshot #3 exited the thigh, "the projectile strikes the left side of the scrotum, causing a very shallow, 3/8 inch linear laceration."

The fatal bullet was Gunshot #4 ... which entered Wallace's body through his right hip and ripped its way through several vital organs ... before coming to rest in his left shoulder area.

According to the report, the bullet perforated Wallace's colon, liver, heart and the upper lobe of his left lung.

Immediately after the shooting Wallace was rushed to Cedars-Sinai Hospital -- where doctors performed an emergency thoracotomy ... but it was too late. Wallace was pronounced dead at 1:15 AM.

According to the report, all 4 of the gunshots traveled through the Suburban passenger door before striking Wallace. Two of the bullets were found on the gurney that transported Wallace to the hospital. Another bullet was discovered at the hospital when the body was turned over after doctors had pronounced him dead.

During the autopsy, the coroner listed Wallace as "morbidly obese." A toxicology test revealed Wallace had no traces of drugs or alcohol in his system at the time of his death.

Wallace's body was eventually ID'd by his mother and wife.

One last thing ... on one of the pages of the autopsy report, there is a note scribbled under the headline "Other Pertinent Information" which reads: "Decedent may be rap singer."