Austin Butler has joined an exclusive set of celebrities -- those who have had items swiped from their homes ... because TMZ has learned cops went to his pad recently after a break-in.

Law enforcement sources tell TMZ ... Austin's security discovered a glass door was shattered on Monday, and, when a guard went inside the house, he noticed the place was ransacked.

We're told responding cops searched the home but didn't find any suspects inside.

Our sources say multiple items were missing, and the guard reported a gun and cash were stolen -- and a full inventory is needed to determine if anything else was snatched during the break-in.

As for Austin, he was out of country when the burglary went down.

So far, no arrests have been made in the case, and the investigation is ongoing.

Our law enforcement sources say it's unclear if Austin's home was targeted or if the actor was just another victim of series of burglaries that have plagued L.A. for years.

We reached out to Austin's reps for comment ... so far, no word back.