The 27-year-old will bow out in what’s tipped to be an “explosive and nailbiting finale”, according to producers.
Jonas, said that playing the title role in the show had been an “incredible experience” but said he was now looking for “new challenges”.
The actor said in a statement: “Over the last three years I have met some wonderful people and have only amazing memories to take with me.”
Foz Allen, the show’s executive producer, added: “Jonas has been a superb Robin Hood who updated the legend for a contemporary audience.
“We cannot confirm the series climax, nor can we guarantee who will survive and who won’t.”
A BBC spokeswoman said Jonas’ exit did not mean the end of the show.
“Robin Hood is more than a man – he is a hero and a legend – so how the legacy unfolds after Jonas leaves is in itself mysterious and intriguing, guaranteed to make fans desperate to find out what happens next.”
Robin Hood is currently filming in Budapest and is expected to return to BBC1 in 2009 to run for 13 episodes.