A sizeable sapphire surrounded by diamonds, the bling was on display at an event promoting her latest film, which also attracted Madonna.
It caught the eye of celeb watchers, leading many to wonder if she's made a formal commitment to her boyfriend, fellow Oscar-winning Spaniard Javier Bardem.
Actually, the lovely señorita has been wearing it for some time.
If Penelope and 40-year-old Javier - her co-star in Vicky Cristina Barcelona - are planning to tie the knot, the discreet pair are keeping it very quiet.
What is clear is that with or without an engagement the 35-year-old's life is going swimmingly.
As Pedro Almodovar, her director in the drama Broken Embraces, put it: "She has… a very handsome, good boyfriend, two Oscar nominations, one Oscar and the respect and admiration of her profession".