The Crown follows both the personal and public lives of Queen Elizabeth II, exploring her reign throughout the decades.
Seasons 1 and 2 of The Crown are set during the 1950s and 60s and see Claire Foy in the role of Britain’s longest-reigning monarch.
For season 3, Olivia Coleman steps into the role as The Crown enters the 1970s and 80s — a tumultuous time for the U.K. during which Thatcher becomes the country’s first woman Prime Minister.
She will first appear in Season 4, which is currently in production.
“I am so excited to be joining the cast and crew of The Crown and to have the opportunity to portray such a complicated and controversial woman,” Anderson said in a statement.
“Thatcher was undoubtedly formidable but I am relishing exploring beneath the surface and, dare I say, falling in love with the icon who, whether loved or despised, defined an era.”
Anderson’s casting extends her relationship with Netflix. In addition to her upcoming role on The Crown, she stars as single mother/sex therapist Jean Milburn in the critically acclaimed Sex Education, which has been renewed for Season 2.
Season 3 of The Crown is set to premiere on Sunday, Nov. 17.