Lori Loughlin and Mossimo Giannulli are now crime victims … because we’ve learned their house was hit by burglars who walked away with a million bucks in jewelry.

It went down January 3 … we’re told Lori and Moss were not home. The break-in and theft were discovered by a housekeeper.

Law Enforcement sources tell TMZ … the thieves smashed a bedroom window at their L.A.- area home. They were dressed in all black and wore masks. Cops know this from surveillance cams. Once inside, they stole Lori’s jewelry box which contained super-expensive bling.

Cops don’t know if Lori and Mossimo were specifically targeted or if this was a random burglary.

Cops believe a South American burglary crew pulled off the heist … apparently, they travel to America, hit locations and then quickly leave the country.

Lori’s camp tells TMZ … Lori’s thankful no one was hurt. Interestingly … Bob Saget‘s death helped put the burglary in perspective for her … she says material stuff isn’t the most important thing in life, it’s family and love.

Since the incident, Lori has beefed up security … they’ll be there around the clock, at least for the time being.