Us Weekly reported that Williams gave birth to a baby girl at a hospital in Palm Beach, Florida.
Serena has been documenting her pregnancy on social media, posting photos of her adorable baby bump throughout the pregnancy.
The 35-year-old first made the announcement on April 20th through her Snapchat.
She even graced the cover of Vanity Fair where she also did a tell-all interview about becoming a mom.
“I don’t know what to do with a baby,” she told the magazine. “I have nothing … I’ve done absolutely nothing for the baby room.”
Williams and Ohania, 34, got engaged in December 2016 but haven't announced a wedding date yet.