Are Paris Hilton and Stavros Niarchos engaged, or is the attention-starved heirhead pulling another sad publicity ploy?

Hilton shocked partygoers Monday night when she arrived at Stacey Bendet’s "Black & White" dinner for her clothing line alice+olivia at Katsuya in L.A. wearing a huge diamond ring on her left hand.

She strolled in with her on-again, off-again Greek - and a ring that looked suspiciously like the fake "diamond" solitaire she once claimed former fiancé Paris Latsis gave her.

(Latsis actually gave her a smaller ring from Cartier.) Either way, Hilton wasn’t being very open about it.

he celebutard acted coy when dinner guests asked about Niarchos and the ring. She spent the night canoodling with Niarchos (who last told Page Six he was "a student"), next to sister Nicky Hilton, Brandon "Greasy Bear" Davis, Michelle Trachtenberg and Mena Suvari. Reps for Hilton and Niarchos didn’t return calls for comment.