The film is set in 1927 and according to the trailer, the plot revolves around the King and Queen of England coming to the estate for a visit.
Over three years after Downton Abbey ended its run on PBS in late 2015, the movie reunites the principal cast of the acclaimed period drama, including Maggie Smith, Hugh Bonneville, Laura Carmichael, Allen Leeche, Elizabeth McGovern, Jim Carter, and Matthew Goode.
The scrambling to get Downton Abbey ready for the royals means the major stars of the show are in the movie.
The plot centers on the visit of the King and Queen of England to the Abbey, with what nearly looks like a "Home Alone"-esque rebellion happening downstairs while upstairs there's bickering between the Dowager Countess and Imelda Staunton's character, Lady Bagshaw, and a potential love interest for Allen Leech".
Now that HBO's Game of Thrones is over (for the time being, anyway), we remind you of your previous TV obsession: Downton Abbey.
The television series Downton Abbey followed the lives of the Crawley family and the servants who worked for them at the turn of the 20 century in an Edwardian English country house.
The door remains open though: Fellowes recently said that a second film could very much be on the cards if all goes well with this one.
Downton Abbey is out on September 13 in the United Kingdom and September 20 in the US.