F.T. Island (Korean: 에프티 아일랜드, or FT아일랜드, short for Five Treasure Island), is a South Korean rock band formed by FNC Entertainment in 2007. The band currently consists of main vocalist Lee Hong-gi, bassist Lee Jae-jin, and drummer Choi Min-hwan. Guitarist Oh Won-bin left the band in 2009 and was replaced by Song Seung-hyun. Former leader Choi Jong-hoon left the band and retired from the entertainment industry on March 14, 2019, while Seung-hyun left the group on December 31, 2019, to pursue his acting career.

F.T. Island debuted on the music television program M Countdown on June 7, 2007, with the single "Love Sick". Their debut studio album, Cheerful Sensibility, was the sixth best-selling of the year and "Love Sick" topped the K-pop charts for eight consecutive weeks. Later that year, the band won the Best New Male Group at the Mnet Asian Music Awards and the Popularity and Rookie of the Year awards at the Golden Disk Awards.

F.T. Island made their Japanese debut on June 8, 2008, with the extended play Prologue of F.T. Island: Soyogi. The band started getting recognition in the country following the release of their third Japanese studio album, Five Treasure Island, in 2011, which topped the Oricon Albums Chart and spawned the single "Flower Rock". Additionally, F.T. Island is the first foreign male band and the first band in 42 years to top the Oricon Daily Charts.

F.T. Island's most well-known songs include "After Love", "Bad Woman", "I Hope", "Hello Hello", "Severely", "I Wish", and the chart-toppers "Love Sick", "Thunder", "Until You Come Back", and "Love Love Love". Considered to be South Korea's first idol band, F.T. Island paved the way for such acts, including label mate N.Flying.