Kate Middleton, Duchess of Cambridge, and Meghan Markle, Duchess of Sussex, will be in attendance, Kensington Palace announced Thursday.
Markle is good friends with Williams. The tennis star and husband Alexis Ohanian attended Markle and Prince Harry's royal wedding in May. Williams accompanied Markle to watch Prince Harry play polo at the Royal Ascot before Wimbledon began.
Middleton will watch the gentlemen's final Sunday with Prince William.
Williams is headed to her 10th Wimbledon final after defeating Germany's Julia Goerges 6-2, 6-4 on Thursday. She'll play for her eighth singles title against Angelique Kerber. Williams has won 23 Grand Slams, one shy of Margaret Court's all-time record of 24 singles Grand Slam titles.