Tarrant has fronted the long-running quiz since its inception, but the 67-year-old recently said: "It's time to take a break."
He added: "It's been a huge part of my life for fifteen years and I've loved every minute of it, but it is time for me to move on from Who Wants to Be a Millionaire.
"It's been the most remarkable journey and I consider myself very fortunate to have been associated with Millionaire from its inception.
"ITV have been fantastic in their support from day one and to see its huge success has been thrilling."
The quiz show offered the chance for contestants to win one million pounds and became a huge hit around the world. It also inspired the Oscar-winning movie Slumdog Millionaire.
Following Tarrant's announcement, ITV said there would be no further specials beyond the ones which have already been planned.
In recent years, the programme has been used as a platform for fundraising celebrity specials.
Tarrant said: "The calibre of the celebrities like Sir Paul McCartney, George Michael, Sir Alex Ferguson, Simon Cowell, Sir Tim Rice, Sir Terry Wogan, Jonathan Ross, Davina McCall, Stephen Fry, Matt Lucas, etc, is just one indication of how much this show has touched a nerve with everybody.
"But of course so much more rewarding for all of us has been, not just the celebrities or even the million-pound winners, but all of the ordinary men and women whose lives have been changed - sometimes forever - by being on the show.
"Thank you all for sitting opposite me. I am privileged to have been a part of it, but do now feel that it is time for me to call it a day."