The Twilight star's boyfriend, Paul Khoury, popped the question during the couple's trip to New Zealand on Dec. 19, the actress revealed on Thursday, alongside an adorable Instagram video of the proposal.
"This is the most beautiful moment I could have ever hoped for. You've successfully made me the happiest, luckiest woman alive," Greene captioned the video. "I can't wait to show you my unfaltering immeasurable love for the rest of our lives. #engaged #? #loveofmylife #futurehusband."
"I promise to put a smile on your face for the rest of our lives. You complete me in ways I didn't even know was possible. I love you more than anything and excited to take this next step in life with you! #foreverlove #myfutrewife ?? #ShesGonnaBeAKhoury," Khoury wrote on his own account.
While the couple -- who have been dating since 2013 -- kept their engagement news quiet until now, they haven't been shy about posting pics from their romantic getaway in Australia and New Zealand.