The tennis pro welcomed a baby girl on Friday - in the middle of the U.S. Open - at St. Mary's Medical Center in West Palm Beach with fiancé Alexis Ohanian.
"Tennis star Serena Williams gives birth to a baby girl weighing 6 pounds, 13 ounces. Mom and baby doing well," WPBF-25 news producer Chris Shepherd announced on Twitter.
The new mom was induced on Thursday night, according to local station CBS 12.
Williams, 35, announced her pregnancy in a bathing suit snap on Snapchat in April with the caption "20 weeks" amid a series of images from the couple's tropical getaway.
The athlete later revealed she had posted the snap publicly by accident - and that it was really only meant for close friends.
Ohanian opened up about how the Olympic champ will be a great mother during an interview with CNBC's "Squawk Box" in early July.
"She's very good at a lot of
things and well on her way to being an awesome mom too," he said.
The techie plans to take six weeks of paternity leave to focus on Williams and their new bundle of joy.
The 23-time major winner previously announced that she would be taking maternity leave for the remainder of 2017. She has said she hopes to return for the Australian Open in January.
Williams was a few weeks pregnant when she beat her sister Venus to win the Australian Open back in January.
She and Ohanian, the co-founder of Reddit, became engaged in December at the Italian restaurant where they first meant.
"This time he made it not by chance / But by choice / Down on one knee / He said 4 words And / isaidyes," she wrote at the time.
She dropped the bombshell news on a thread on her love's website, Reddit.
The two have yet to announce a wedding date.