The 37-year-old star - who already has a two-year-old daughter with her husband Travis Browne - announced at San Diego Comic-Con that she is expecting her second child.
Rousey was actually in San Diego to promote her debut graphic novel, Expect The Unexpected, and the former mixed martial artist also decided to share her pregnancy news with the world.
During a conversation with panel host Dave Bautista, she said of her latest project: "It's like Knocked Up meets John Wick, and also a romantic comedy.
"The main character is a super nerd, assassin for hire, who's also a hopeless romantic. Unfortunately, all people that she sees, she's about to kill. So just having a hard time connecting with anyone."
Rousey and her husband tied the knot in 2017, and the loved-up couple welcomed their daughter, La'akea, back in September 2021.
The former UFC star, who has also enjoyed some success as an actress, previously suggested that her daughter could follow in her mother's footsteps one day.
Speaking to PEOPLE, Rousey shared: "Oh, she's definitely going to be tough. She doesn't respond to pain so much.
"She just fell and scraped her knee today and she was just like ... she didn't even cry. She just kind of grunts it out!
"The world isn't ready for this little girl."
Rousey also confessed to suffering from "mom guilt" after she returned to work.
The Furious 7 star said: "I was having a better and better experience, that I felt worse and worse about being away from her. And so, the mom guilt was compounding by the day, and I think that was more difficult than any part of the experience itself."
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