Netflix is introducing its new Geralt of Rivia.
Hemsworth, 34, will replace Henry Cavill, 41, as Geralt in the new season.
The teaser shows Geralt (Hemsworth) walking with his horse through a misty forest and ends with a glimpse of his face.
The Witcher is a fantasy drama based on the Andrzej Sapkowski book series, which was previously adapted as a video game franchise.
The show follows Geralt, a monster hunter known as a Witcher, as the strives to protect the princess Ciri (Freya Allan) with the help of the sorceress Yennefer (Anya Chalotra).Season 4 started production in April and will shoot back-to-back with the show's fifth and final season.
"It is with huge pride that we begin shooting our penultimate season of The Witcher with a stellar cast, including some exciting new additions, led by Liam Hemsworth as Geralt of Rivia," showrunner Lauren Schmidt Hissrich said at the time. "We're thrilled to be able to bring Andrzej Sapkowski's books to an epic and satisfying conclusion. It wouldn't be our show if we didn't push our family of characters to their absolute limit -- stay tuned to see how the story ends."
Hemsworth is known for playing Gale Hawthorne in the Hunger Game movies and Josh Taylor on Neighbours.
