Mike 'The Situation' Sorrentino -- I'm Done with Rehab

The Situation has CHECKED OUT of the Cirque Lodge rehab center in Utah ... where he was receiving treatment for substance abuse ... TMZ has learned.

TMZ broke the story ... Mike Sorrentino checked in to the famous treatment center several weeks ago ... claiming he wanted to "get control of a prescription medication problem I had due to exhaustion."

Sitch was spotted out moments ago at a nearby airport ... and even took a photo with a fan who happened to be on his flight.

Now comes the biggest test of all ... when Sitch re-enters the danger zone to tape the next season of "Jersey Shore."