Charlize Theron stood out on the Cannes red carpet in a gorgeous yellow Dior gown for the Thursday premiere of Mad Max: Fury Road. The actress posed with her costars and also had boyfriend Sean Penn by her side. The couple walked the carpet arm in arm and held hands as they made their way up the stairs. While Sean and Charlize had more than a few picture-perfect moments, it was the rock on her ring finger that really turned heads. Charlize showed off the massive teardrop diamond by putting her left hand on her hip and throwing her arm over Sean's shoulder, perhaps trying to tell us something? The duo have been dating for more than a year and reportedly got engaged over the holidays, and though neither party has spoken out about their relationship status, Charlize did recently gush about Sean being the love of her life. So what do you think? Could that rock be Charlize's engagement ring?