Vic Mensa‘s pleading guilty to possession of a controlled substance, but he won’t do any time behind bars after striking a deal with prosecutors … TMZ has learned.

Kendra Glover, a rep for the Loudoun County Commonwealth’s Attorney, tells TMZ … Mensa pled guilty to one count of possession of a Schedule III controlled substance, which is a Class 1 misdemeanor.

We’re told as part of the plea deal he got 12 months in jail, but that was suspended — meaning instead of serving it behind bars, he’ll have a year of unsupervised probation.

Vic will also have to take a substance abuse assessment, perform 25 hours of community service, and pay a $1k fine. BTW, he’ll get 50 percent off that fine if he successfully completes the other probation terms.

As we’ve reported, Vic was arrested back in January at Dulles International airport for going through customs with a stash of shrooms.

Vic tells TMZ … “In this case, I have decided to plead guilty to a misdemeanor charge. I have been extremely vocal about my mental health, the culture at large and access to mental health treatment. It is important to note the extensive research being done on the topic of psilocybin [shrooms] and the many significant movements underway for legalization and decriminalization.

He continues, “Esteemed universities such as Johns Hopkins, University of California, NYU, Mount Sinai School of Medicine and The Imperial College of London have all immersed themselves in years-long research programs with full departments and centers dedicated to this work. Unfortunately, our laws have not kept up with the research showing that psychedelic plants and compounds can be successfully used to treat otherwise treatment-resistant mental illness.”