Armstrong thanked the fans and crew for their support
Jonas Armstrong, who plays Robin Hood in the BBC's remake of the classic tale, is to leave the show at the end of the third series.
The 27-year-old, who is currently filming in Budapest, said playing Robin Hood was an "incredible experience" but he was looking for "new challenges".
According to producers, the Irish-born actor will bow out in an explosive and nail-biting finale.
How the story will unfold after Armstrong leaves remains a mystery.
"Over the last three years I have met some wonderful people and have only amazing memories to take with me," the actor said in a statement.
A BBC spokeswoman said the finale would be "intriguing and guaranteed to make fans desperate to find out what happens next".
Foz Allen, the show's executive producer, added: "We cannot confirm the series climax, nor can we guarantee who will survive and who won't."
The third series of Robin Hood will be shown on BBC One next year, and will run for 13 episodes.