Are Cameron Diaz and Benji Madden engaged?

Could wedding bells be in Cameron Diaz's future?

The "Bad Teacher" actress was spotted sporting a ring on her left hand this week that has some wondering if she and boyfriend Benji Madden are engaged.

Speculation began after Diaz, 42, attended the Academy's Hollywood Costume luncheon on Wednesday in Los Angeles wearing the sparkler.

An eyewitness told People (which has a close-up photo of the jewelry) that Diaz was "showing off the ring and often playing with it" at the event. That evening, she and Madden, 35, had dinner with friends in Beverly Hills, where she also reportedly showed off the ring.

The actress and Good Charlotte rocker were first linked together this past spring, and have reportedly gotten serious in the months since. "It's early, but they have talked about marriage," an insider told People back in July.