She and Bill Gates divorced in 2021, and she called the end "incredibly painful."
The Microsoft co-founder, who first appeared on the Forbes 400 list in 1986, is currently worth an estimated $100 billion.
The philanthropist also told Gayle King about her views on Jeffrey Epstein: "He was evil personified."
The announcement comes weeks after Bill and Melinda Gates announced that they were divorcing after 27 years of marriage.
Gates said he left his post on the Microsoft board in 2020 to focus on philanthropy.
The billionaire philanthropists have been married for 27 years.
Bill and Melinda Gates warned that the coronavirus pandemic could lead to “immunity inequality” if only the wealthiest people have access to the vaccine.
The philanthropists, who have donated $1.75 billion to coronavirus research, argued that global health needs to be a top priority.
“Equality can’t wait, and no one in a position to act should either," the philanthropist wrote on Wednesday.
Sofia Coppola, Toni Morrison, Lucy Liu and others share the best advice they got from their fathers that you can apply to your own career.