"We wanted to close the doors of Downton Abbey when it felt right and natural for the storylines to come together," executive producer Gareth Neame said in a statement, "and when the show was still being enjoyed so much by its fans."
Julian Fellowes, the show's writer and creator, said the journey was amazing for everyone involved.
"People ask if we knew what was going to happen when we started to make the first series," Fellowes said, "and the answer is that, of course we had no idea."
Speculation of the show's demise hit a high earlier this month when star Maggie Smith, who plays the dowager Countess of Grantham, hinted that she wouldn't return after season six.
"They say this is the last one, and I can't see how it could go on," Smith told the Sunday Times, adding, "I mean, I certainly can't keep going. To my knowledge, I must be 110 by now. We're into the late 1920s."
Shortly after, a publicist for the show issued a statement saying that Smith's comments had been misinterpreted.
The Emmy and Golden Globe award-winning drama follows the lives and loves of the Crawley family and its servants in their stately Georgian country house. It was set in 1912 when it launched back in September 2010.
Since then, Downton has become of of the U.K.'s biggest exports, airing in than 250 countries.
Season five, which concluded on PBS in North America earlier this month, was seen by 25.5 million people, the studio said.
Production on season six is currently underway, but it's not clear when it will air.
When it does, Neame is promising "a final season full of all the usual drama and intrigue, but with the added excitement of discovering how and where they all end up."
Fellowes, meantime, is signed on to write a new NBC series called The Gilded Age which follows the upper crust of New York's society in the 1800s.