The 25-year-old, who plays ex-con Eli Dingle in the rural serial, announced his decision to quit the soap at the premiere of Michael Cain's new crime thriller film Harry Brown, in which Gilgun portrays a character called Kenny.
He told the press on the red carpet: "It will be sad to leave - I've made a lot of good friends there but I think it is time to move on as far as my career is concerned."
Of what he'll miss about working with the programme, he added: "The routine. You get into a massive routine working on a soap. I get to act every day, which is brilliant. And there are massive personalities there. I'll miss my friends."
An Emmerdale spokeswoman this afternoon confirmed: "We can confirm that Joseph Gilgun will be leaving Emmerdale early next year but we're not ruling out the possibility of him returning to the show. We wish Joe all the very best for the future."
Gilgun - who first appeared in Emmerdale in 2006 after signing a one-month contract - is due to finish filming and make his screen departure in the early part of 2010.