Yui (born March 26, 1987), stylized as YUI or yui, is a Japanese singer-songwriter and multi-instrumentalist. In her solo career, she sold more than 5 million physical copies in Japan. She is popular in Japan and in surrounding countries, ranking number one in 2011 Count Down TV "Dearest Female Artist" and Music Station "Artist You Most Want to Marry" polls, as well as Radio Television Hong Kong's "Most Popular Japanese Artist".

Born and raised in Fukuoka prefecture, she played live at various locations in her hometown before being noticed by Sony Music Japan when she was 17 years old, and released her debut single months later. Her singles, however, were only met with moderate success until the breakout "Good-bye Days", which charted for 44 weeks on Oricon and marked her as one of the Japanese music industry's rising stars. Since Yui's debut album, From Me to You, each of her soloist album releases has topped the charts, with at least one single reaching number one on the Oricon charts from 2007 until her second hiatus in 2012, including five straight from mid-2008 to late 2010. After retiring from music as a soloist in 2012, she formed the band Flower Flower in 2013.