Kelly Monaco Burglar -- Robbed of His Freedom

The guy who pilfered Kelly Monaco's Las Vegas penthouse back in April is heading to the slammer -- he was just sentenced to serve 12 to 30 months behind bars.

Merrill Wetter pled guilty to burglary back in June, after he broke into Kelly's pad at the Planet Hollywood Resort and Casino on April 23.

As part of his plea deal, Wetter will also have to pay Kelly $5,000 in restitution, as well as a $25 court fee and a $150 DNA fee.

Wetter -- who will serve his time in the Nevada State Prison -- has already served 138 days.