Melissa King -- the chick formerly known as Miss Delaware Teen USA until she resigned in the wake of a porn scandal -- is officially on probation ... after copping a plea in her underage alcohol case.
The 19-year-old disgraced beauty queen plead guilty in a Maryland court to one count of possession of alcohol while under the age of 21 ... stemming from an incident last summer when cops found a bottle of Captain Morgan in her truck.
As part of the deal, King was sentenced to 1 year of unsupervised probation -- meaning if she stays out of trouble for the next 365 days, she stays out of jail.
Fun Fact -- King's lawyer told the court Melissa plans to go to college.
We have a feeling she'll be very popular in college.