"A" is a song by the South Korean girl group Rainbow. It was released on August 12, 2010, and was later included on their second mini album So Girls.

Rainbow (Korean: 레인보우) was a South Korean girl group formed in 2009 by DSP Media. The group is composed of seven members: Woori, Seungah, Jaekyung, Noeul, Yoonhye, Jisook and Hyunyoung. They released their debut EP Gossip Girl on November 12, 2009, and since released two studio albums and five extended plays, In October 2016, DSP Media announced that Rainbow would disband after seven years because their contracts expired. In November 2019, the group was re-formed for their tenth anniversary.