Downton Abbey is a British historical drama television series set in the early 20th century, created and co-written by Julian Fellowes. It first aired in the United Kingdom on ITV on 26 September 2010 and in the United States on PBS, which supported its production as part of its Masterpiece Classic anthology, on 9 January 2011. The show ran for fifty-two episodes across six series, including five Christmas specials.

The series, set on the fictional Yorkshire country estate of Downton Abbey between 1912 and 1926, depicts the lives of the aristocratic Crawley family and their domestic servants in the post-Edwardian era, and the effects the great events of the time have on their lives and on the British social hierarchy. These events include news of the sinking of the Titanic (first series); the outbreak of the First World War, the Spanish influenza pandemic and the Marconi scandal (second series); the Irish War of Independence leading to the formation of the Irish Free State (third series); the Teapot Dome scandal (fourth series); and the British general election of 1923 and the Beer Hall Putsch (fifth series). The sixth and final series introduces the rise of the working class during the interwar period and hints at the eventual decline of the British aristocracy.

Downton Abbey has received acclaim from television critics and numerous accolades, including a Golden Globe Award for Best Miniseries or Television Film and a Primetime Emmy Award for Outstanding Miniseries or Movie. It was recognised by Guinness World Records as the most critically acclaimed English-language television series of 2011. It earned 27 Primetime Emmy Award nominations after its first two series, the most for any international television series in the awards' history. It was the most watched television series on both ITV and PBS, and became the most successful British costume drama since the 1981 television serial of Brideshead Revisited.

On 26 March 2015, Carnival Films and ITV announced that the sixth series would be the last; it aired on ITV between 20 September 2015 and 8 November 2015. The final episode, the annual Christmas special, was broadcast on 25 December 2015. A film adaptation, a continuation of the series, was confirmed on 13 July 2018 and released in the United Kingdom on 13 September 2019, and in the United States on 20 September 2019. A second feature film, Downton Abbey: A New Era, was released in the United Kingdom on 29 April 2022 by Universal Pictures, and in the United States and Canada on 20 May 2022 by Focus Features. A third film is in production.