Alexia Fernandez of People reported guests for the high-profile wedding are expected to start arriving in Louisiana on Wednesday. Beyonce and Jay Z headline the rumored list of attendees.
Williams and Ohanian, who started dating in 2015, welcomed a baby girl, Alexis Olympia Ohanian Jr., in September. She is the couple's first child.
The 36-year-old American tennis sensation is the owner of 23 Grand Slam singles titles, including the 2017 Australian Open, which she won during the early stages of her pregnancy.
In August, Williams told Rob Haskell of Vogue she's got no plans to walk away from the sport despite the major changes in her personal life.
"It's hard to figure out what the end of your tennis career should look like," she said. "I used to think I'd want to retire when I have kids, but no. I'm definitely coming back. Walking out there and hearing the crowd, it may seem like nothing. But there's no better feeling in the world."
She added: "Obviously, if I have a chance to go out there and catch up with Margaret [Court], I am not going to pass that up. If anything, this pregnancy has given me a new power."
Court holds the all-time record for Grand Slam singles titles with 24, one more than Williams.
Ohanian, 34, is a New York City native who founded Reddit with Steve Huffman in 2005. He also co-founded Initialized Capital, a multimillion dollar venture capital fund, with Garry Tan in 2011.