(TMZ) -- The L.A. burglars really hit the big one this time -- breaking into Mariah Carey's mansion and making off with $50,000 worth of stuff ... TMZ has learned.

Law enforcement sources tell TMZ Mariah's crib was hit around 3 AM Thursday. It appears they got in through a window or door on an upper floor ... a ladder was found in the backyard.

Surprisingly, TMZ was told the crooks didn't make off with any fabulous jewelry. Instead, they bagged up $50k worth of purses and sunglasses. Here's the thing ... as expensive as Mimi's taste is, that's probably less than 10 items total.

In any event, TMZ was told no one was home at the time -- Mariah is in NYC -- and although the burglars tripped a silent alarm ... her security didn't discover the break-in until about 6 or 7 AM.

Cops are investigating, and they've got a glut of these cases now. As TMZ reported ... Jason Derulo, Alanis Morissette, David Spade, Emmy Rossum and Scott Disick -- to name just a few -- have all been hit this year.

Welcome to the club, Mariah.

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