Kevin Feige made the announcement at Disney’s D23 Conference on Saturday.
Feige said The Eternals “focuses on a group of ancient, everlasting beings, the film will span eons in their lives.”
Harington is playing a non-Eternal named Dane Whitman.
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The Game of Thrones star joins a cast that includes Angelina Jolie (Thena), Madden (Icarus), Kumail Nanjiani (Kingo), Lauren Ridloff (Makkari), Brian Tyree Henry (Phastos), Lia McHugh (Sprite), Don Lee (Gilgamesh), Gemma Chan (Sersi), Barry Keoghan (Druid) and Salma Hayek (Ajak).
The Rider’s Chloe Zhao is directing the film.
During Marvel’s presentation at San Diego Comic-Con, Madden said: “The Eternals are a race of immortal aliens sent to Earth by the Celestials to protect humankind from the Deviants.”
Jolie said: “I’m so excited to be here. I’m going to work 10 times harder because I think what it means to be a part of the MCU, what it means to be an Eternal, to be a part of this family, I know what we all need to do.
“We have all read the script. We have all know what the task ahead is and we are all going to be working very, very hard. I’m training. I am thrilled. Thank you so much.”
Many Game of Thrones fans took to Twitter to celebrate the reunion of Harington and Madden after the casting news was announced.
The film is set for release on Nov. 6, 2020.
— With files from the Associated Press