John Stamos and his fiance Caitlin McHugh are getting married this weekend -- TMZ has learned -- but they had to spend time with cops because she's the victim of a jewelry heist.
Law enforcement sources tell TMZ, Caitlin was staying at the Beverly Hills Hotel Friday when she left -- presumably for dinner -- and came back to find burglars had broken into her bungalow and stolen around $165,000 in jewelry.
What's worse ... we're told the jewelry was on loan from the Neil Lane collection, which means she's on the hook to the jeweler.
We're told Caitlin called John and he rushed over to the hotel to comfort his pregnant fiance.
Cops tell us there was no sign of forced entry.
So far, no suspects.