The actress will take on the role as Britain's former Prime Minister, who served as the leader of the Conservative Party and sat in office from 1979 to 1990. And while Thatcher was a controversial figure, Anderson, 51, admitted she's looking forward to exploring what lies "beneath the surface" of the character.
"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," she said in a statement on social media. "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."
The hit Netflix show will see a shake-up of its principal cast for its upcoming third series, as it explores the next decade of the monarchy, following the second season's climax in 1964.
Olivia Colman will take over following Claire Foy's celebrated portrayal of Queen Elizabeth II, Tobias Menzies will replace Matt Smith as Prince Philip and Emerald Fennell is Camilla Shand, who would eventually become Camilla, Duchess of Cornwall. Helena Bonham Carter also joins the cast as Princess Margaret in place of Vanessa Kirby.
Season three of "The Crown" drops on 17 November, while the fourth series is currently in production.