The actor, 78, starred as detective DCI Tom Barnaby in the crime drama from 1997.
However, he left the show after 14 years.
It has now been announced that he will be back in a one-off programme that will mark 25 years of the popular drama.
Fans will get a peek behind the scenes as well as taking a trip down memory lane in Midsomer Murders – 25 Years of Mayhem, which will feature new and old cast members, including Nettles, Neil Dudgeon, Nick Hendrix, Annette Badland and Tamzin Outhwaite, who was a guest star.
ITV said that the documentary “will shine a light on the fictional English county of Midsomer, looking at the numerous mysterious crimes and murders to befall it, as well as paying tribute to the exceptional on and off screen talent who have played pivotal roles in keeping millions of viewers glued to their screens since 1997”.
Executive producer Mark Robinson said in a statement: “So much has changed on British television in the last 25 years – but Midsomer Murders has remained a constant throughout.
"It’s testament to the high regard the viewers have for this series - a television institution with enduring appeal and a loyal fan base who love its eccentric take on the classic whodunnit.
"It’s been a privilege to hear about its journey from those who have brought it to our screens."
Nettles starred in Midsomer Murders from 1997, the year the show started, to 2011.
Fans of the series are counting down until the special airs.
“So excited!” one posted on Twitter.
Another person tweeted: “Love, love, love this show! One of the best murder mystery series ever created!”
An air date has yet to be announced.
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