Hollywood's leading man George Clooney may be off the market.

The 52-year-old Oscar-winning actor's girlfriend, human rights lawyer Amal Alamuddin, was recently seen flashing a "massive" ring on her left ring finger, sources told E! News.

The raven-haired Alamuddin, 36, and Clooney were reportedly spotted recently dining at Malibu restaurant Nobu. They were joined by former supermodel Cindy Crawford and her husband Rande Gerber.

According to E! News, when fellow award-winning actor Edward Norton approached their table during the meal, Clooney and Alamuddin told him, "We're engaged!"

This is not the first time Clooney has popped the question. He was married to actress Talia Balsam from 1989 to 1993, and later swore off marriage.

After his divorce, Clooney dated a string of women, including British model Lisa Snowden, Canadian waitress Maria Bertrand, soap opera star Krista Allen, onetime "Fear Factor" winner Sarah Larson, Italian model Elisabetta Canalis, and former WWE wrestler Stacy Keibler.

Clooney and Alamuddin were first photographed together in London in October 2013.