Decca Records is a British record label established in 1929 by Edward Lewis after his acquisition of a gramophone manufacturer, The Decca Gramophone Company. It set up an American subsidiary under the Decca name, which became an independent company just before the Second World War. The American spin-off became a subsidiary of MCA Inc. in 1962. Known for its technical innovations, the British parent company grew to become the second most successful recording company in Britain and celebrated fifty years of existence in 1979, shortly before being sold to PolyGram. Both Decca and its former subsidiary were subsequently acquired by Universal Music.

Decca and its American spin-off both built up strong catalogues of popular music. In their first two decades, their artists included Gertrude Lawrence, George Formby, Jack Hylton and Vera Lynn in Britain and Bing Crosby, Al Jolson, the Andrews Sisters and the Mills Brothers in the US. Later performers in their popular catalogues included in the US Bill Haley & His Comets and Buddy Holly plus in the UK Elvis Presley (licensed from RCA Records), Tommy Steele, Lonnie Donegan, Chuck Berry (licensed from Chess Records), Johnny Cash (licensed from Sun Records), Eddie Cochran (licensed from Liberty Records), and the Rolling Stones.

In the classical sphere, Decca became a major player after the Second World War, building up a large catalogue of symphonic, operatic, chamber and other music. Between 1958 and 1965 the company made what has been widely described as the gramophone's greatest achievement – the first complete recording to be released of Wagner's operatic tetralogy, Der Ring des Nibelungen (The Nibelung's Ring). Decca's advanced technological expertise offered recorded sound of unprecedented realism in the mid-20th century, and it was an early adapter of digital technology.

The origins of the Decca Record Company were not in making records but in making the gramophones on which to play them. Shortly before the First World War the first Decca product was offered to the public: the "Decca Dulcephone" a portable gramophone, retailing at two guineas (£2.10 in decimal currency, and equivalent to about £250 in 2023 terms). It was manufactured by the musical instrument makers Barnett Samuel and Sons Ltd, a company founded in 1869. There are various theories about the derivation of the name "Decca", but the musicologist Robert Dearling describes it as "a word whose origins are lost".

In the 1920s, the company changed its name to "The Decca Gramophone Company" and it was floated on the stock market in 1928. Edward Lewis, a London stockbroker, acted for the company, despite his reservations about its business model:

Lewis tried to convince Decca's board that the way forward was to expand into record production and manufacture, and recommended buying out the struggling Duophone Record Company in south London, arguing that "with the well-known Decca trademark and ... distributing organization ... a Decca record would surely succeed where others were failing". The Decca directors were unpersuaded and Lewis raised enough capital to acquire not only Duophone but Decca itself.

On 7 February 1929, the Decca Record Company's first discs were recorded: dance music performed by Ambrose and the May Fair Orchestra. The first classical recording took place four days later at the Chenil Galleries in Chelsea, and featured the violist Cecil Bonvallot in an arrangement of J. S. Bach's Komm, süßer Tod. Among the fledgling company's releases in its first year were a set of numbers from William Walton and Edith Sitwell's Façade conducted by the composer and recited by Sitwell and Constant Lambert, and a set of Handel Concerti grossi conducted by Ernest Ansermet, who made more than a hundred recordings for Decca between then and 1968. A premiere recording of Delius's Sea Drift conducted by Julian Clifford was in less than ideal sound, but marked Decca's first association with the baritone Roy Henderson which lasted for the rest of his career.

The Great Depression of the 1930s hit Decca hard. Lewis, although he remained nominally merely a board member, effectively took over the direction of the company and at his instigation Decca made substantial cuts in the prices of its records. In 1930, Decca acquired the British rights to the German Polydor label, gaining access to a wide range of classical recordings. During the decade Decca also bought the British rights to the Fonit [it] and Ultraphon catalogues, but sold its French subsidiary to Edison Bell. Decca bought a majority shareholding in the American Brunswick Record Company from the Warner Brothers film studios; its catalogue contained recordings by leading popular artists such as Bing Crosby, Guy Lombardo and Al Jolson. Decca established an American subsidiary, Decca Records US, in 1934, funded and chaired by Lewis and led by Jack Kapp, Milton Rackmil and E. F. Stevens. American Decca boosted its presence in the popular market by signing the Andrews Sisters and the Mills Brothers. As the Second World War loomed, Lewis, foreseeing a freeze of his overseas assets, sold his holdings in the US company.