Idris, 42, has reprised his role as DCI John Luther for two hour-long specials, which will be filmed in and around London.
Idris posed with a thumbs up as he shared the selfie with fans at 5:32am. He said: "First day back to set of John Luther....stand by East London."
The picture left many fans excited, with one declaring: "Can't wait for the new season of Luther!! The best detective show on the planet!!"
Another said: "I'm so glad I'm awake to see this. I'm screaming with delight and doing my happy dance! #JohnLutherIsBack."
It was announced in November last year that Idris would reprise his role for the BBC crime drama, and it came as welcome news for fans, who thought the third series - which wrapped up in July - would be the very last.
Writer and creator Neil Cross, said at the time: "Ever since we said goodbye to John Luther on Southwark Bridge, there's hardly been a minute when I didn't wonder what happened next. So I decided to find out.
"We're putting the band back together; Luther is coming back where he belongs. Back to the BBC. Back to London. And back to work."
The series three finale was a gripping and nail-biting episode, as viewers watched the shock death of Luther's sidekick Justin Ripley.
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