Lee Ji-eun (Korean: 이지은; born May 16, 1993), also known by her stage name IU (아이유), is a South Korean singer-songwriter and actress. She signed with LOEN Entertainment (now Kakao Entertainment) in 2007 as a trainee and debuted as a singer at the age of fifteen with the EP Lost and Found (2008). Although her follow-up albums brought mainstream success, it was only after the release of "Good Day", the lead single from her 2010 album Real, that she achieved national stardom. "Good Day" went on to spend five consecutive weeks at the top of South Korea's Gaon Digital Chart, and in 2019, it was ranked number one on Billboard's "100 Greatest K-Pop Songs of the 2010s" list.

With the success of her 2011 albums, Real+ and Last Fantasy, IU established herself as a formidable force on the music charts of her native country and further cemented her girl next door image as Korea's "little sister". Her musical style matured and evolved with subsequent releases, deviating from mainstream K-pop styles, exploring and mixing various music genres, with IU exerting more creative control over her music, both as lyricist and producer, at the same time consistently retaining her dominance on South Korean music charts. Her 2020 single "Eight" (prod. by Suga) became her first to reach number one on Billboard's World Digital Song Sales chart.

Aside from her music career, IU has ventured into acting and hosting radio and television shows, starting with a supporting role in the hit teen series Dream High (2011). IU's role as a desperate office worker in My Mister (2018) received critical acclaim, and she earned her first Best Actress in Television nomination at the 55th Baeksang Arts Awards.

IU has released a total of five studio albums and nine EPs, five of which have reached number one on the Gaon Album Chart, and thirty-one number-one singles, making her the artist with the most number-one songs in South Korea. One of the best-selling solo acts in the group-dominated K-pop industry, IU became the first solo female K-pop act to perform at the Olympic Gymnastics Arena during the Seoul leg of her 2018 dlwlrma concert tour for her 10th anniversary and also the first Korean female artist to hold a solo concert, The Golden Hour, at Seoul Olympic Stadium in Seoul on September 17 and 18, 2022.

Rolling Stone named her the 135th greatest singer of all time in a 2023 ranking. She has been included five times in the top ten of Forbes magazine's annual Korea Power Celebrity list since 2012 and attained a peak ranking of number three that year. In 2014, Billboard recognized IU as the all-time leader of its K-pop Hot 100 with the most number-one songs and the artist with the most weeks at the number-one position on the chart. She was named Gallup Korea's Singer of the Year in 2014 and in 2017. In 2024, media outlets such as NME and Billboard referred to IU as the "Queen of K-pop," highlighting her widespread influence and consistent success in the industry.