Fernando Valenzuela's cause of death has been revealed -- the Los Angeles Dodgers legend died of septic shock.
TMZ Sports has obtained the 1981 World Series champion's death certificate ... which listed decompensated alcoholic cirrhosis and nonalcoholic steatohepatitis cirrhosis as underlying causes.
The medical examiner also suspects Valenzuela suffered from Creutzfeldt-Jakob disease ... a rare brain disorder.
The 63-year-old's occupation is listed as "sports broadcaster.