Davis confirmed the news on Twitter saying, "Sooo proud!!! Honoring and elevating these powerful, worthy Queens with respect."
The Showtime series will focus on the personal and political lives of first ladies throughout America's history. The first season will feature Michelle Obama, Eleanor Roosevelt and Betty Ford, according to Variety.
The latter two roles have yet to be cast.
"Having Viola Davis play Michelle Obama is a dream come true, and we couldn't be luckier to have her extraordinary talent to help launch this series," said Jana Winograde, President of Entertainment at Showtime, in a statement.
Davis is getting ready to say goodbye to ABC's "How to Get Away with Murder," which will air its final episode in the spring.