Girls' Generation (Hangul: 소녀시대; RR: Sonyeo Sidae), also known as SNSD, is a South Korean girl group formed by SM Entertainment. The group is composed of eight members: Taeyeon, Sunny, Tiffany, Hyoyeon, Yuri, Sooyoung, Yoona, and Seohyun. Originally a nine-piece group, Jessica later departed from the group in September 2014. Deemed one of the prominent figures of the Korean Wave and one of the most popular K-pop acts internationally, the group's immense popularity in their native country South Korea has earned them numerous accolades and the honorific nicknames "The Nation's Girl Group" and "The Nation's Singers".

Girls' Generation debuted in August 2007 with the single "Into the New World" from their Korean eponymous debut album. Though the album gained some attention, it was not until 2009 that the group rose to fame with the single "Gee", which claimed the top spot on KBS' Music Bank for a record-breaking nine consecutive weeks and was named the most popular song of the 2000s in South Korea by Melon. Girls' Generation further consolidated their popularity on the South Korean music scene with the follow-up singles "Genie", "Oh!", and "Run Devil Run", which were released in mid-2009 and early 2010. Their second Korean studio album, Oh! (2010), won the Golden Disc award for Album of the Year and the group became the only female artist to win the grand prize in the 2010s.

In mid-2010, Girls' Generation signed with Nayutawave Records (present-day EMI Records Japan) to venture into the Japanese music scene. Their 2011 eponymous Japanese debut album peaked atop the Japanese Oricon Albums Chart and became the first album by a non-Japanese girl group to be certified "Million" by the RIAJ. The group's third Korean studio album, The Boys, was released in October 2011 and became the best-selling album of 2011 in South Korea with sales of over 380,000 copies. An English version of the single "The Boys" was released by Interscope Records in an attempt to expand the group's endeavor to the global music scene. The group's fourth Korean studio album, I Got a Boy (2013), was supported by the single "I Got a Boy", which was subjected to major attention from Western media following its winning the Video of the Year award at the inaugural YouTube Music Awards. Their fifth Korean studio album, Lion Heart, was released in 2015 and they became the first artist to accumulate over 100 wins on all of the music programs in South Korea. In 2017, Girls' Generation released their sixth Korean studio album, Holiday Night, to commemorate the group's tenth anniversary.

The group's signature musical styles are characterized as electropop and bubblegum pop, though their sounds have varied widely, incorporating various genres including hip hop, R&B, and EDM. In 2017, Billboard honoured Girls' Generation as the best "K-pop Girl Group of the Past Decade". They are the first Asian girl group to achieve five music videos with over 100 million views on YouTube: "Gee", "I Got a Boy", "The Boys", "Mr. Taxi", and "Oh!". In Japan, they became the first non-Japanese girl group to have three number-one albums on the Japanese Oricon Albums Chart, and their three Japanese concert tours attracted a record-breaking 550,000 spectators, more than any other Korean girl group.