She did not reveal why she decided to forgo the delayed summer games.
“There’s a lot of reasons that I made my Olympic decision,” the 39-year-old American said. “I don’t really want to … I don’t feel like going into them today. Maybe another day. Sorry.”
The Olympics are scheduled to start on July 23.
She has won four Olympic gold medals over her prestigious career after making her Games debut at Sydney in 2000.
Williams won gold in the doubles at Sydney in 2000 as well as gold in the singles and women’s doubles at London 2012 and another gold at the doubles at Beijing 2008.
Williams will look to win a record-tying 24th major and eighth Wimbledon title when the famous tournament begins on Tuesday when she faces Aliaksandra Sasnovich of Belarus in the first round.