Law enforcement sources tell TMZ ... Tom and Rita's estate was burglarized a few weeks ago, with thieves smashing through glass to get inside a guest house on their property.

We're told the incident went down in broad daylight while the actor couple was out of town ... and an alarm triggered by the broken glass wasn't enough to stop the thieves from going inside.

Still, the good news here is the thieves did NOT make it inside the main house.

Unclear what, if anything, was stolen and how much those items might be worth. Tom and Rita will need to go through their belongings to figure out what's missing.

Our sources say it doesn't appear Tom and Rita were targeted ... instead, we're told this looks like the work of one of the many crews in the area burglarizing at will.

The case remains under police investigation ... so far, no arrests.

Tom and Rita are the latest celebs to fall victim to the huge uptick in burglaries in and around Los Angeles ... joining Bhad Bhabie, Sarah Hyland and Marlon Wayans, among others.

Our sources say many of these criminals are getting braver, with some even tying up victims inside their homes.