Are Cameron Diaz and Benji Madden Engaged?

Cameron Diaz, Benji Madden "have talked about marriage," says a source

A smiling Cameron Diaz arrived at the Academy's Hollywood Costume luncheon Wednesday sporting a sparkling ring - leading guests to wonder if it could be a sign of an engagement to boyfriend Benji Madden.

During the luncheon in Los Angeles, Diaz, 42, took a seat at a table with Gwyneth Paltrow, where she was "casually and constantly twirling her ponytail, showing off the ring and often playing with it," says an eyewitness.

Cameron Diaz stepped out sporting some new ring bling, sparking rumours she's engaged to boyfriend Benji Madden. Photo: Wire Image

That evening, the couple had dinner with friends at Italian hot spot Madeo, in Beverly Hills, where the actress flaunted her ring, a source tells WHO. "They arrived together with Benji driving. Cameron showed off her new ring and was smiling," the source says. "They enjoyed dinner for several hours."

A loved up Cameron Diaz and Benji Madden enjoyed a romantic holiday in Europe earlier this year. Photo: Splash

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After spending time with Diaz's family in Florida in July, the couple took their relationship to the next level. Madden, 35, appears to have moved in with Diaz in her Beverly Hills house, another source tells WHO.

"Since she started dating Benji, Cameron has changed in a very positive way. She can't stop smiling and seems much happier," the source adds. "Benji has lived with Cameron for the past couple of months. They act like they can't get enough of each other and spend a lot of time together. During the days, they often share a workout. At night, they often stay at home and cook."

RELATED: Cameron Diaz and Benji Madden: Why They're Ready To Wed

The two have also "talked about marriage," according to an entertainment source.

"For a girl who was happy being single, Cameron seems to have fallen in love," the source says. "She is really happy. The relationship is deep and she wants people to know it."

Madden appears equally smitten, and when asked about his romantic relationship in August, he told WHO, "I'm really happy right now."

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Reps for both stars have not commented.