Robert Downey Jr's Son Indio Charged with Felony Drug Possession

Robert Downey Jr.'s son Indio has been charged with felony possession of a controlled substance ... TMZ has learned.

As TMZ previously reported, the 20-year-old was arrested in June after cops noticed he was a passenger in a car in West Hollywood ... smoking something out of a pipe. Authorities say Indio -- who appeared in "Kiss Kiss Bang Bang" -- was in possession of cocaine.

Sources tell TMZ ... Indio -- a first-time offender -- is automatically entitled to a drug diversion program.

In addition to the felony, Indio has been charged with misdemeanor possession of drug paraphernalia.

Robert Downey Jr. thanked the L.A. County Sheriff's Dept. for what he called "their intervention."

Robert famously struggled with addiction and then overcame it in a spectacular way.