Chandler shared the exciting news as well, revealing some special details about the moment it all went down.
"Proposing in her very favorite place in the zoo, surrounded by animals, seemed like the perfect way to embark on this incredible new chapter in our lives. Bee, I love you more than anything in this world and I always will. Happy Birthday."
There have been a bunch of celebrities that have commented their congratulations on the post, including Millie Bobby Brown, who wrote: "Aww congratulations and happy birthday Bindi."
The official Australia Zoo Instagram page added: "We’re so excited for you both! This is the best news ever!!"
Younger brother Robert Irwin also took to his Instagram to post a photo with the happy couple, captioning it: "I am beyond happy for you two. You are true soulmates and have always been so completely perfect for each other. Love you both and congratulations."
At the 21-year-old's birthday party, Bindi wished that her late dad, iconic Steve Irwin, could be with her.
"What gets to me are those moments when I’d love him to be here to share what we’re doing," Bindi recently told Stellar. "It could be when my brother is receiving an accolade for his photography, or it might be at the end of the day when we’re having dinner and laughing.
"I’ll think: 'I wish Dad was here for this.' But he’s just not there."
We're SO happy for the bride and groom-to-be!!!