America's got talent, but it no longer has Sharon Osbourne ... 'cause the AGT judge says she's QUITTING the TV show for good.
Osbourne -- who has been with "America's Got Talent" since Season 2 -- cryptically announced her exit from the show via Twitter on Tuesday, saying "My darling @howardstern, money is not the reason I'm not returning to @nbcagt, it's because ..."
It's unclear if she was informing Howard about her departure ... or blaming him.
Sources from NBC say Sharon's exit is a surprise to them as well ... claiming they have not been personally informed of her departure yet.
You'll recall ... the series shook things up this season when it added Howard Stern to its judges table -- they even moved the show from L.A. to NYC to accommodate him.