This is a list of songs that were either recorded or written by ABBA, but which were never released during the bands' active years (1972–1983) for various reasons. Some of the songs were released later in their entirety or as parts of the track "Abba Undeleted" (included in the box set Thank You for the Music, 1994), while some of the songs were released as part of solo projects.

Several newspapers and magazines believed ABBA would make a comeback in 1988. In an interview with an unknown ABBA member, 4 new songs were stated to have been recorded: "It's Been Swell", "It's Alright Darling", "I Just Wasn't Thinking" and "Something On My Mind". It's unknown if this was actually true or if these songs were ever recorded by ABBA.

"Dream World" (working title: "Dream Land") is a song recorded in September 1978 with shared vocals by Fältskog and Lyngstad and solo passage by Fältskog. The song was recorded during sessions for the Voulez-Vous album. Composers Benny Andersson and Björn Ulvaeus decided, however, that "Dream World" was not suitable for release, and instead, agreed to scrap the recording.

The melody and chord sequence of the middle-eight of "Dream World" were re-used, with different lyrics, as the bridge for the middle-eight of the song "Does Your Mother Know", later released as the second single from Voulez-Vous

In the 1980s, the song was heard for the first time in a Swedish radio programme featuring ABBA's engineer Michael B. Tretow, and subsequently found its way onto a bootleg album.

In 1994, "Dream World" was released in Sweden, Germany and Australia as a promotional-only CD-single with other ABBA rarities to advertise the Thank You for the Music four CD box-set, which also contained the track.

The version of the song released in 1994 differs from the version heard in the radio show in that its fairground-like synthesiser intro fades in rather than starting abruptly. However this is because the tape from which the track was taken was partly destroyed. Voulez-Vous Deluxe Edition, released in May 2010, contains the track with its original beginning. It is unknown how the full intro was resurrected from the partially destroyed tape.

It was reported just before its 1994 release that Benny and Björn were in the studio remixing the track, and hence it is most probably a new mixdown of the song done expressly in 1994. Indeed, it exhibits a certain "digital" sound suggesting it was mixed down to a digital recorder as opposed to previously released songs from this period which were mixed onto analog tape.

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