"Excited to share that I will now be paying for 3 weddings😂 I feel so blessed to say that our third child is on the way and it's a girl!! I love you so much @laur_akins. WG and AJ, y'all are gonna be the best big sisters! Bring on the crazy," Rhett wrote in his caption.
Rhett and his wife are already the parents of two girls: Willa Gray, 3, and Ada James, 23 months.
"We decided we didn't have enough princess dresses around the house so we're adding another Akins baby girl to the family early next year," Rhett's wife, Lauren Akins, wrote. "We are absolutely over the moon for our baby girl! Our girls cannot wait to meet their little sister."
Lauren also shared photos of the couple shooting off cannons to reveal a little girl was on the way.
The Nashville couple married in 2012 after being childhood friends.
Rhett released his latest album Center Point Road in May. The country superstar is currently on his Very Hot Summer Tour, which runs through October.