John Stamos has been in rehab for more than 2 weeks now ... TMZ has learned.
Stamos checked into a residential treatment facility on June 24, according to our sources. That was 12 days after his DUI bust in Beverly Hills.
Sources tell TMZ ... Stamos' issues are not a recent development. We're told he's getting treatment for a substance abuse problem that "developed over a period of time."
You'll recall ... when Stamos was arrested, the officers felt he was in dire need of medical attention and rushed him to a hospital. He was released the next day.