TMZ Studios has a new documentary -- "TMZ Investigates Matthew Perry and the Secret Celebrity Drug Ring" -- which drops today, Tuesday, on Hulu.

Several celebrities, including Kelly Osbourne, talk about how it's common knowledge in Hollywood that doctors provide specific drugs to celebrities. For her part, Kelly was able to score Vicodin and Oxy from various Hollywood doctors. And get this ... she was 13 at the time and the doctors never told her mom and dad what they were prescribing their daughter.

It gets even worse ... Kelly would go to the pharmacy to fill the Rx's without a parent present ... we're talking about a 13-year-old getting hard, addictive drugs from a pharmacy -- no questions asked.

The documentary explores how doctors, enablers and even rehab centers are turning celebrities into addicts ... sometimes with fatal consequences.