Chuck Berry died from natural causes ... TMZ has learned.

We're told Berry's personal doctor will sign off on the death certificate that the cause of death was natural, and there will be no autopsy. By the way, various diseases would still classify the cause of death as "natural."

Police responded to a medical emergency Saturday at Berry's home 45 miles from St. Louis. Attempts to resuscitate the 90-year-old legend were unsuccessful.

Chuck was a pioneer for rock 'n' roll in both style and sound. He had a string of hits through his long, decorated career including "Johnny B. Goode," "Roll Over Beethoven," "Maybellene" and tons more.

RIP