AOA (Korean: 에이오에이; an acronym for Ace of Angels) is a South Korean girl group formed by FNC Entertainment. The original 2012 eight-member line-up included: Choa, Jimin, Yuna, Youkyung, Hyejeong, Mina, Seolhyun, and Dohwa. The group has been inactive since 2020, following a series of scandals within the group's lineup and the members' departures from FNC.

AOA began their career simultaneously promoting as a dance group and band, and officially debuted in July 2012 with the release of the single album Angel's Story. In early 2013, the band unit AOA Black released their official single titled "MOYA" to moderate success. They released their first EP in June 2014, and that year they also debuted in Japan under Universal Music Japan. The group found nationwide success in 2014 after a series of hit songs that established them as one of the leading girl groups of their era. "Heart Attack" debuted at the top of several charts after its release, became one of the most downloaded songs of 2015, and became one of the longest charting singles on Melon's top 100 chart.

Following a series of consistent success, AOA debuted a second promotional unit, AOA Cream, in 2016. The group would later release their first Korean language studio album in January 2017, and a few months later, held their first headlining Korean concert "Ace Of Angels" at Olympic Hall in Seoul. Among the groups' biggest hits are "Miniskirt", "Short Hair", "Like a Cat", "Heart Attack", "Give Me the Love", "Good Luck", "Excuse Me", and "Bingle Bangle".

The eight members were introduced individually through teaser photos from July 16 to 23 (in order: Seolhyun, Choa, Hyejeong, Dohwa, Yuna, Mina, Jimin, & Youkyung).

AOA were introduced with a 'transformer' concept, which the group described meant they would promote alternately as a band with various members playing instruments and as a dance group. Explaining the concept of their debut, FNC revealed that seven members are "full angels": Seolhyunari (Seolhyun), Choaya (Choa), Hyejeong.Linus (Hyejeong), Chanmi T.T (Dohwa), Yunaria (Yuna), Minaring (Mina), and leader Jiminel (Jimin), while Youkyung (or "Y") is listed as a "half-angel/half-mortal" as she is only a member when the group promotes as a band, thus they were known as a "7+1" group. The song and music video for their debut title track "Elvis" was released on July 30. The group began promotions with their debut stage on August 9 on M Countdown and then Music Bank on August 10 to minimal success.

Two months after their debut, FNC confirmed that the group would be making a comeback with a second single album "Wanna Be" on October 10. The album cover was released along with the announcement, which depicted the eight members as different fictional characters. Hyejeong, Jimin, Choa, Yuna, Dohwa, Mina, Seolhyun and Youkyung dressed as characters from Kill Bill, Léon, Legally Blonde, Tomb Raider, Harry Potter, Breakfast at Tiffany's, Romeo and Juliet, and The Fifth Element respectively.

In the latter half of 2012, it was confirmed that five-member band unit, AOA Black would perform a stage in the first week of promotions for "Get Out". AOA Black made their first comeback appearance on the October 10 broadcast of KM's Music Triangle and performed the band version of "Get Out" for the first time. The band made their second appearance on the October 12 broadcast of Music Bank.

The following year, on July 11, it was announced that AOA Black would be releasing their debut song, "MOYA". The third single album and "MOYA" music video were released on July 26 and AOA Black had their first comeback stage on KBS Music Bank on the same day. A few months later, the dance group released "Confused," alongside another single album, Red Motion, which was released on October 13 to moderate success. At the end of that year, AOA appeared on FNC Entertainment's reality show "Cheongdam-dong 111," which depicted dramatized scenarios behind the scenes of the entertainment company among its artists, employees and other staff.