While reps for both actors have not yet responded to inquiries regarding the ring, the sparkler prompted many sources to speculate that the couple has gotten engaged.
The Lone Ranger star, 50, and Heard, 27, made their red carpet debut as a couple Saturday at the Art of Elysium gala at L.A.'s Skirball Center.
The couple met on the set of their 2011 film The Rum Diary. They worked together again in Heard's latest movie London Fields in which Depp has a cameo.
Celebrity Couples of 2014 [PHOTOS]