Britney Spears Claims Someone Stole All Her Jewelry

Britney Spears says she's been the victim of theft ... telling her millions of Instagram followers someone stole all her jewelry -- but, she hasn't filed a police report yet.

The singer-songwriter took to IG Sunday night and shared a video she took where she shows her fans a series of small empty drawers ... claiming it's where she kept her valuable trinkets and now they're all gone.

She still has a couple small pieces -- including a Virgin Mary pendant -- in the set-up ... but, basically, she's saying her bling's pretty much MIA.

Spears writes in the caption she's scared to buy new jewelry after the alleged theft ... 'cause she's terrified it'll go missing. Plus, some of the pieces in her collection carried a ton of sentimental value -- making them truly irreplaceable.

Despite the video, it seems Brit hasn't gone to the authorities yet. Law enforcement sources tell us she hasn't reported a theft to the sheriff's department, as Page Six first reported.

Of course, Spears is very active on social ... sharing tons of photos and videos including a recent one where she swam completely naked in the water off a tropical beach.

She's posted multiple times since telling her fans her jewelry got taken BTW ... sharing more dancing clips and a still from the flick "Kill Bill: Vol. 2."