The 22-year-old shared a snap of herself, Chandler, who held a sonogram, and an Aldabra tortoise at Australia Zoo.
She captioned the photo, "Baby girl, you are our world.
"Our beautiful daughter is now about the same size as a hatchling Aldabra tortoise and is as healthy as can be. We can’t wait for her arrival next year."
Friends, family and fans were quick to share their congratulations with the couple with Bindi's brother Robert Irwin writing, "I can’t wait to meet my niece!"
Chandler, 23, also shared a sweet message that read, "I love you and our daughter more than anything."
Fellow Wildlife Warrior Luke Reavley wrote, "So exciting! You’re going to be an incredible Mum!"
Actress Emmy Perry said, "Oh my goodness, that is so exciting! I look forward to meeting to meeting your little girl!"
While some fans speculated on the baby girl's name, one follower asked, "A girl named Stevie, perhaps?"
"Name her Stevie!" another excited fan said, while someone else said, "I'd like to guess a possible name. Stephanie."
The pair announced they're expecting last month, Bindi shared a snap of herself and Chandler holding a tiny khaki shirt with the caption reading, "Baby Wildlife Warrior due 2021.
"Chandler and I are proud to announce that we’re expecting! It’s an honour to share this special moment in our lives with you. Though I’m still in my first trimester, we really want you to be part of our journey from the beginning of this new life chapter.
"We couldn’t wait to share the news as this beautiful little being has become the most important part of our lives. Your support means the world to us. Please let me know your best advice and send good vibes & prayers to our little sweetheart. Love & light."
The pair married in a surprise ceremony in March after moving their original wedding date due to the coronavirus pandemic.